diff --git a/mozilla/layout/forms/nsTextControlFrame.cpp b/mozilla/layout/forms/nsTextControlFrame.cpp
index 980e912a494..b024003fed9 100644
--- a/mozilla/layout/forms/nsTextControlFrame.cpp
+++ b/mozilla/layout/forms/nsTextControlFrame.cpp
@@ -1779,63 +1779,58 @@ nsTextControlFrame::Reflow(nsPresContext*   aPresContext,
                               aStatus);
 }
 
-NS_IMETHODIMP
-nsTextControlFrame::GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsTextControlFrame::GetPrefSize(nsBoxLayoutState& aState)
 {
-  if (!DoesNeedRecalc(mPrefSize)) {
-     aSize = mPrefSize;
-     return NS_OK;
-  }
+  if (!DoesNeedRecalc(mPrefSize))
+     return mPrefSize;
 
 #ifdef DEBUG_LAYOUT
   PropagateDebug(aState);
 #endif
 
-  aSize.width = 0;
-  aSize.height = 0;
+  nsSize pref(0,0);
 
   // XXXbz this is almost certainly wrong.
   PRBool collapsed = PR_FALSE;
   IsCollapsed(aState, collapsed);
   if (collapsed)
-    return NS_OK;
+    return pref;
 
-  nsresult rv = CalcIntrinsicSize(aState.GetRenderingContext(), aSize);
-  NS_ENSURE_SUCCESS(rv, rv);
-  AddBorderAndPadding(aSize);
-  AddInset(aSize);
+  nsresult rv = CalcIntrinsicSize(aState.GetRenderingContext(), pref);
+  NS_ENSURE_SUCCESS(rv, pref);
+  AddBorderAndPadding(pref);
+  AddInset(pref);
 
-  mPrefSize = aSize;
+  mPrefSize = pref;
 
 #ifdef DEBUG_rods
   {
     nsMargin borderPadding(0,0,0,0);
     GetBorderAndPadding(borderPadding);
     nsSize size(169, 24);
-    nsSize actual(aSize.width/15, 
-                  aSize.height/15);
+    nsSize actual(pref.width/15, 
+                  pref.height/15);
     printf("nsGfxText(field) %d,%d  %d,%d  %d,%d\n", 
            size.width, size.height, actual.width, actual.height, actual.width-size.width, actual.height-size.height);  // text field
   }
 #endif
 
-  return NS_OK;
+  return pref;
 }
 
-
-
-NS_IMETHODIMP
-nsTextControlFrame::GetMinSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsTextControlFrame::GetMinSize(nsBoxLayoutState& aState)
 {
   // XXXbz why?  Why not the nsBoxFrame sizes?
-  return nsBox::GetMinSize(aState, aSize);
+  return nsBox::GetMinSize(aState);
 }
 
-NS_IMETHODIMP
-nsTextControlFrame::GetMaxSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsTextControlFrame::GetMaxSize(nsBoxLayoutState& aState)
 {
   // XXXbz why?  Why not the nsBoxFrame sizes?
-  return nsBox::GetMaxSize(aState, aSize);
+  return nsBox::GetMaxSize(aState);
 }
 
 NS_IMETHODIMP
diff --git a/mozilla/layout/forms/nsTextControlFrame.h b/mozilla/layout/forms/nsTextControlFrame.h
index 508b48775ee..14871eeeb89 100644
--- a/mozilla/layout/forms/nsTextControlFrame.h
+++ b/mozilla/layout/forms/nsTextControlFrame.h
@@ -86,9 +86,9 @@ public:
                     const nsHTMLReflowState& aReflowState,
                     nsReflowStatus&          aStatus);
 
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMaxSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMaxSize(nsBoxLayoutState& aBoxLayoutState);
   NS_IMETHOD GetAscent(nsBoxLayoutState& aBoxLayoutState, nscoord& aAscent);
 
   DECL_DO_GLOBAL_REFLOW_COUNT_DSP(nsTextControlFrame, nsStackFrame)
diff --git a/mozilla/layout/generic/nsFrame.cpp b/mozilla/layout/generic/nsFrame.cpp
index 9e4e79fb021..9be07ba3ee0 100644
--- a/mozilla/layout/generic/nsFrame.cpp
+++ b/mozilla/layout/generic/nsFrame.cpp
@@ -5781,110 +5781,96 @@ nsFrame::RefreshSizeCache(nsBoxLayoutState& aState)
   return rv;
 }
 
-NS_IMETHODIMP
-nsFrame::GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsFrame::GetPrefSize(nsBoxLayoutState& aState)
 {
-  DISPLAY_PREF_SIZE(this, aSize);
+  nsSize size(0,0);
+  DISPLAY_PREF_SIZE(this, size);
   // If the size is cached, and there are no HTML constraints that we might
   // be depending on, then we just return the cached size.
   nsBoxLayoutMetrics *metrics = BoxMetrics();
   if (!DoesNeedRecalc(metrics->mPrefSize)) {
-     aSize = metrics->mPrefSize;
-     return NS_OK;
+    size = metrics->mPrefSize;
+    return size;
   }
 
-  aSize.width = 0;
-  aSize.height = 0;
-
   PRBool isCollapsed = PR_FALSE;
   IsCollapsed(aState, isCollapsed);
-  if (isCollapsed) {
-    return NS_OK;
-  } else {
-    // get our size in CSS.
-    PRBool completelyRedefined = nsIBox::AddCSSPrefSize(aState, this, metrics->mPrefSize);
+  if (isCollapsed)
+    return size;
 
-    // Refresh our caches with new sizes.
-    if (!completelyRedefined) {
-       RefreshSizeCache(aState);
-       metrics->mPrefSize = metrics->mBlockPrefSize;
+  // get our size in CSS.
+  PRBool completelyRedefined = nsIBox::AddCSSPrefSize(aState, this, size);
 
-       // notice we don't need to add our borders or padding
-       // in. That's because the block did it for us.
-       // but we do need to add insets so debugging will work.
-       AddInset(metrics->mPrefSize);
-       nsIBox::AddCSSPrefSize(aState, this, metrics->mPrefSize);
-    }
+  // Refresh our caches with new sizes.
+  if (!completelyRedefined) {
+    RefreshSizeCache(aState);
+    size = metrics->mBlockPrefSize;
+
+    // notice we don't need to add our borders or padding
+    // in. That's because the block did it for us.
+    // but we do need to add insets so debugging will work.
+    AddInset(size);
+    nsIBox::AddCSSPrefSize(aState, this, size);
   }
 
-  aSize = metrics->mPrefSize;
-
-  return NS_OK;
+  metrics->mPrefSize = size;
+  return size;
 }
 
-NS_IMETHODIMP
-nsFrame::GetMinSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsFrame::GetMinSize(nsBoxLayoutState& aState)
 {
-  DISPLAY_MIN_SIZE(this, aSize);
+  nsSize size(0,0);
+  DISPLAY_MIN_SIZE(this, size);
   // Don't use the cache if we have HTMLReflowState constraints --- they might have changed
   nsBoxLayoutMetrics *metrics = BoxMetrics();
   if (!DoesNeedRecalc(metrics->mMinSize)) {
-     aSize = metrics->mMinSize;
-     return NS_OK;
+    size = metrics->mMinSize;
+    return size;
   }
 
-  aSize.width = 0;
-  aSize.height = 0;
-
   PRBool isCollapsed = PR_FALSE;
   IsCollapsed(aState, isCollapsed);
-  if (isCollapsed) {
-    return NS_OK;
-  } else {
-    // get our size in CSS.
-    PRBool completelyRedefined = nsIBox::AddCSSMinSize(aState, this, metrics->mMinSize);
+  if (isCollapsed)
+    return size;
 
-    // Refresh our caches with new sizes.
-    if (!completelyRedefined) {
-       RefreshSizeCache(aState);
-       metrics->mMinSize = metrics->mBlockMinSize;
-       AddInset(metrics->mMinSize);
-       nsIBox::AddCSSMinSize(aState, this, metrics->mMinSize);
-    }
+  // get our size in CSS.
+  PRBool completelyRedefined = nsIBox::AddCSSMinSize(aState, this, size);
+
+  // Refresh our caches with new sizes.
+  if (!completelyRedefined) {
+    RefreshSizeCache(aState);
+    size = metrics->mBlockMinSize;
+    AddInset(size);
+    nsIBox::AddCSSMinSize(aState, this, size);
   }
 
-  aSize = metrics->mMinSize;
-
-  return NS_OK;
+  metrics->mMinSize = size;
+  return size;
 }
 
-NS_IMETHODIMP
-nsFrame::GetMaxSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsFrame::GetMaxSize(nsBoxLayoutState& aState)
 {
-  DISPLAY_MAX_SIZE(this, aSize);
+  nsSize size(NS_INTRINSICSIZE, NS_INTRINSICSIZE);
+  DISPLAY_MAX_SIZE(this, size);
   // Don't use the cache if we have HTMLReflowState constraints --- they might have changed
   nsBoxLayoutMetrics *metrics = BoxMetrics();
   if (!DoesNeedRecalc(metrics->mMaxSize)) {
-     aSize = metrics->mMaxSize;
-     return NS_OK;
+    size = metrics->mMaxSize;
+    return size;
   }
 
-  aSize.width = NS_INTRINSICSIZE;
-  aSize.height = NS_INTRINSICSIZE;
-
   PRBool isCollapsed = PR_FALSE;
   IsCollapsed(aState, isCollapsed);
-  if (isCollapsed) {
-    return NS_OK;
-  } else {
-    metrics->mMaxSize.width = NS_INTRINSICSIZE;
-    metrics->mMaxSize.height = NS_INTRINSICSIZE;
-    nsBox::GetMaxSize(aState, metrics->mMaxSize);
-  }
+  if (isCollapsed)
+    return size;
 
-  aSize = metrics->mMaxSize;
+  size = nsBox::GetMaxSize(aState);
+  metrics->mMaxSize = size;
 
-  return NS_OK;
+  return size;
 }
 
 NS_IMETHODIMP
diff --git a/mozilla/layout/generic/nsFrame.h b/mozilla/layout/generic/nsFrame.h
index 97c4932897d..c2e00e3396f 100644
--- a/mozilla/layout/generic/nsFrame.h
+++ b/mozilla/layout/generic/nsFrame.h
@@ -359,9 +359,9 @@ public:
   virtual ContentOffsets CalcContentOffsetsFromFramePoint(nsPoint aPoint);
 
   // Box layout methods
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMaxSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMaxSize(nsBoxLayoutState& aBoxLayoutState);
   NS_IMETHOD GetFlex(nsBoxLayoutState& aBoxLayoutState, nscoord& aFlex);
   NS_IMETHOD GetAscent(nsBoxLayoutState& aBoxLayoutState, nscoord& aAscent);
   NS_IMETHOD SetIncludeOverflow(PRBool aInclude);
diff --git a/mozilla/layout/generic/nsGfxScrollFrame.cpp b/mozilla/layout/generic/nsGfxScrollFrame.cpp
index 169068feead..b7f8cf55c94 100644
--- a/mozilla/layout/generic/nsGfxScrollFrame.cpp
+++ b/mozilla/layout/generic/nsGfxScrollFrame.cpp
@@ -296,12 +296,12 @@ GetScrollbarMetrics(nsBoxLayoutState& aState, nsIBox* aBox, nsSize* aMin,
                "computations");
   
   if (aMin) {
-    aBox->GetMinSize(aState, *aMin);
+    *aMin = aBox->GetMinSize(aState);
     nsBox::AddMargin(aBox, *aMin);
   }
  
   if (aPref) {
-    aBox->GetPrefSize(aState, *aPref);
+    *aPref = aBox->GetPrefSize(aState);
     nsBox::AddMargin(aBox, *aPref);
   }
 }
@@ -429,9 +429,9 @@ nsHTMLScrollFrame::ReflowScrolledFrame(const ScrollReflowState& aState,
   nscoord availWidth = aState.mReflowState.mComputedWidth + paddingLR;
 
   if (aAssumeVScroll) {
-    nsSize vScrollbarPrefSize;
-    mInner.mVScrollbarBox->GetPrefSize(NS_CONST_CAST(nsBoxLayoutState&, aState.mBoxState),
-                                       vScrollbarPrefSize);
+    nsSize vScrollbarPrefSize = 
+      mInner.mVScrollbarBox->GetPrefSize(NS_CONST_CAST(nsBoxLayoutState&, 
+                                                       aState.mBoxState));
     availWidth = PR_MAX(0, availWidth - vScrollbarPrefSize.width);
   }
   // pixel align the content
@@ -913,8 +913,7 @@ nsMargin nsGfxScrollFrameInner::GetDesiredScrollbarSizes(nsBoxLayoutState* aStat
   nsMargin result(0, 0, 0, 0);
 
   if (mVScrollbarBox) {
-    nsSize size;
-    mVScrollbarBox->GetPrefSize(*aState, size);
+    nsSize size = mVScrollbarBox->GetPrefSize(*aState);
     nsBox::AddMargin(mVScrollbarBox, size);
     if (IsScrollbarOnRight())
       result.left = size.width;
@@ -923,8 +922,7 @@ nsMargin nsGfxScrollFrameInner::GetDesiredScrollbarSizes(nsBoxLayoutState* aStat
   }
 
   if (mHScrollbarBox) {
-    nsSize size;
-    mHScrollbarBox->GetPrefSize(*aState, size);
+    nsSize size = mHScrollbarBox->GetPrefSize(*aState);
     nsBox::AddMargin(mHScrollbarBox, size);
     // We don't currently support any scripts that would require a scrollbar
     // at the top. (Are there any?)
@@ -1051,94 +1049,87 @@ nsXULScrollFrame::GetAscent(nsBoxLayoutState& aState, nscoord& aAscent)
   return rv;
 }
 
-NS_IMETHODIMP
-nsXULScrollFrame::GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsXULScrollFrame::GetPrefSize(nsBoxLayoutState& aState)
 {
 #ifdef DEBUG_LAYOUT
   PropagateDebug(aState);
 #endif
 
+  nsSize pref = mInner.mScrolledFrame->GetPrefSize(aState);
+
   nsGfxScrollFrameInner::ScrollbarStyles styles = GetScrollbarStyles();
 
-  nsSize vSize(0,0);
-  if (mInner.mVScrollbarBox &&
-      styles.mVertical == NS_STYLE_OVERFLOW_SCROLL) {
-     mInner.mVScrollbarBox->GetPrefSize(aState, vSize);
-     nsBox::AddMargin(mInner.mVScrollbarBox, vSize);
-  }
-   
-  nsSize hSize(0,0);
-  if (mInner.mHScrollbarBox &&
-      styles.mHorizontal == NS_STYLE_OVERFLOW_SCROLL) {
-     mInner.mHScrollbarBox->GetPrefSize(aState, hSize);
-     nsBox::AddMargin(mInner.mHScrollbarBox, hSize);
-  }
-
-  nsresult rv = mInner.mScrolledFrame->GetPrefSize(aState, aSize);
-
   // scrolled frames don't have their own margins
 
-  aSize.width += vSize.width;
-  aSize.height += hSize.height;
+  if (mInner.mVScrollbarBox &&
+      styles.mVertical == NS_STYLE_OVERFLOW_SCROLL) {
+    nsSize vSize = mInner.mVScrollbarBox->GetPrefSize(aState);
+    nsBox::AddMargin(mInner.mVScrollbarBox, vSize);
+    pref.width += vSize.width;
+  }
+   
+  if (mInner.mHScrollbarBox &&
+      styles.mHorizontal == NS_STYLE_OVERFLOW_SCROLL) {
+    nsSize hSize = mInner.mHScrollbarBox->GetPrefSize(aState);
+    nsBox::AddMargin(mInner.mHScrollbarBox, hSize);
+    pref.height += hSize.height;
+  }
 
-  AddBorderAndPadding(aSize);
-  AddInset(aSize);
-  nsIBox::AddCSSPrefSize(aState, this, aSize);
-
-  return rv;
+  AddBorderAndPadding(pref);
+  AddInset(pref);
+  nsIBox::AddCSSPrefSize(aState, this, pref);
+  return pref;
 }
 
-NS_IMETHODIMP
-nsXULScrollFrame::GetMinSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsXULScrollFrame::GetMinSize(nsBoxLayoutState& aState)
 {
 #ifdef DEBUG_LAYOUT
   PropagateDebug(aState);
 #endif
 
-  aSize = mInner.mScrolledFrame->GetMinSizeForScrollArea(aState);
+  nsSize min = mInner.mScrolledFrame->GetMinSizeForScrollArea(aState);
 
   nsGfxScrollFrameInner::ScrollbarStyles styles = GetScrollbarStyles();
      
   if (mInner.mVScrollbarBox &&
       styles.mVertical == NS_STYLE_OVERFLOW_SCROLL) {
-    nsSize vSize(0,0);
-    mInner.mVScrollbarBox->GetMinSize(aState, vSize);
+     nsSize vSize = mInner.mVScrollbarBox->GetMinSize(aState);
      AddMargin(mInner.mVScrollbarBox, vSize);
-     aSize.width += vSize.width;
-     if (aSize.height < vSize.height)
-        aSize.height = vSize.height;
+     min.width += vSize.width;
+     if (min.height < vSize.height)
+        min.height = vSize.height;
   }
         
   if (mInner.mHScrollbarBox &&
       styles.mHorizontal == NS_STYLE_OVERFLOW_SCROLL) {
-     nsSize hSize(0,0);
-     mInner.mHScrollbarBox->GetMinSize(aState, hSize);
+     nsSize hSize = mInner.mHScrollbarBox->GetMinSize(aState);
      AddMargin(mInner.mHScrollbarBox, hSize);
-     aSize.height += hSize.height;
-     if (aSize.width < hSize.width)
-        aSize.width = hSize.width;
+     min.height += hSize.height;
+     if (min.width < hSize.width)
+        min.width = hSize.width;
   }
 
-  AddBorderAndPadding(aSize);
-  AddInset(aSize);
-  nsIBox::AddCSSMinSize(aState, this, aSize);
-  return NS_OK;
+  AddBorderAndPadding(min);
+  AddInset(min);
+  nsIBox::AddCSSMinSize(aState, this, min);
+  return min;
 }
 
-NS_IMETHODIMP
-nsXULScrollFrame::GetMaxSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsXULScrollFrame::GetMaxSize(nsBoxLayoutState& aState)
 {
 #ifdef DEBUG_LAYOUT
   PropagateDebug(aState);
 #endif
 
-  aSize.width = NS_INTRINSICSIZE;
-  aSize.height = NS_INTRINSICSIZE;
+  nsSize max(NS_INTRINSICSIZE, NS_INTRINSICSIZE);
 
-  AddBorderAndPadding(aSize);
-  AddInset(aSize);
-  nsIBox::AddCSSMaxSize(aState, this, aSize);
-  return NS_OK;
+  AddBorderAndPadding(max);
+  AddInset(max);
+  nsIBox::AddCSSMaxSize(aState, this, max);
+  return max;
 }
 
 #if 0 // XXXldb I don't think this is even needed
@@ -1902,8 +1893,7 @@ nsXULScrollFrame::AddRemoveScrollbar(nsBoxLayoutState& aState, nsRect& aScrollAr
      if (mInner.mNeverHasHorizontalScrollbar || !mInner.mHScrollbarBox)
        return PR_FALSE;
 
-     nsSize hSize;
-     mInner.mHScrollbarBox->GetPrefSize(aState, hSize);
+     nsSize hSize = mInner.mHScrollbarBox->GetPrefSize(aState);
      nsBox::AddMargin(mInner.mHScrollbarBox, hSize);
 
      mInner.SetScrollbarVisibility(mInner.mHScrollbarBox, aAdd);
@@ -1919,8 +1909,7 @@ nsXULScrollFrame::AddRemoveScrollbar(nsBoxLayoutState& aState, nsRect& aScrollAr
      if (mInner.mNeverHasVerticalScrollbar || !mInner.mVScrollbarBox)
        return PR_FALSE;
 
-     nsSize vSize;
-     mInner.mVScrollbarBox->GetPrefSize(aState, vSize);
+     nsSize vSize = mInner.mVScrollbarBox->GetPrefSize(aState);
      nsBox::AddMargin(mInner.mVScrollbarBox, vSize);
 
      mInner.SetScrollbarVisibility(mInner.mVScrollbarBox, aAdd);
@@ -1982,8 +1971,7 @@ nsXULScrollFrame::LayoutScrollArea(nsBoxLayoutState& aState, const nsRect& aRect
 
   PRInt32 flags = NS_FRAME_NO_MOVE_VIEW;
 
-  nsSize minSize(0,0);
-  mInner.mScrolledFrame->GetMinSize(aState, minSize);
+  nsSize minSize = mInner.mScrolledFrame->GetMinSize(aState);
   
   if (minSize.height > childRect.height)
     childRect.height = minSize.height;
diff --git a/mozilla/layout/generic/nsGfxScrollFrame.h b/mozilla/layout/generic/nsGfxScrollFrame.h
index 757f3cc56af..700f27466a1 100644
--- a/mozilla/layout/generic/nsGfxScrollFrame.h
+++ b/mozilla/layout/generic/nsGfxScrollFrame.h
@@ -453,9 +453,9 @@ public:
   // nsIBox methods
   NS_DECL_ISUPPORTS
 
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMaxSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
+  virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMaxSize(nsBoxLayoutState& aBoxLayoutState);
   NS_IMETHOD GetAscent(nsBoxLayoutState& aBoxLayoutState, nscoord& aAscent);
 
   NS_IMETHOD DoLayout(nsBoxLayoutState& aBoxLayoutState);
diff --git a/mozilla/layout/generic/nsIFrame.h b/mozilla/layout/generic/nsIFrame.h
index ce83be44e9f..ccdcc016984 100644
--- a/mozilla/layout/generic/nsIFrame.h
+++ b/mozilla/layout/generic/nsIFrame.h
@@ -100,10 +100,10 @@ struct nsMargin;
 typedef class nsIFrame nsIBox;
 
 // IID for the nsIFrame interface 
-// 42728a19-b289-48b8-b6f4-1a46b719a63b
+// c822dca6-310c-433d-a1d0-d5b5b1cdce1f
 #define NS_IFRAME_IID \
-{ 0x42728a19, 0xb289, 0x48b8, \
-  { 0xb6, 0xf4, 0x1a, 0x46, 0xb7, 0x19, 0xa6, 0x3b } }
+{ 0xc822dca6, 0x310c, 0x433d, \
+  { 0xa1, 0xd0, 0xd5, 0xb5, 0xb1, 0xcd, 0xce, 0x1f } }
 
 /**
  * Indication of how the frame can be split. This is used when doing runaround
@@ -1816,9 +1816,27 @@ NS_PTR_TO_INT32(frame->GetProperty(nsGkAtoms::embeddingLevel))
     vAlign_Bottom
   };
 
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)=0;
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)=0;
-  NS_IMETHOD GetMaxSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)=0;
+  /**
+   * This calculates the minimum size required for a box based on its state
+   * @param[in] aBoxLayoutState The desired state to calculate for
+   * @return The minimum size
+   */
+  virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState) = 0;
+
+  /**
+   * This calculates the preferred size of a box based on its state
+   * @param[in] aBoxLayoutState The desired state to calculate for
+   * @return The preferred size
+   */
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState) = 0;
+
+  /**
+   * This calculates the maximum size for a box based on its state
+   * @param[in] aBoxLayoutState The desired state to calculate for
+   * @return The maximum size
+   */    
+  virtual nsSize GetMaxSize(nsBoxLayoutState& aBoxLayoutState) = 0;
+
   NS_IMETHOD GetFlex(nsBoxLayoutState& aBoxLayoutState, nscoord& aFlex)=0;
   NS_HIDDEN_(nsresult)
     GetOrdinal(nsBoxLayoutState& aBoxLayoutState, PRUint32& aOrdinal);
diff --git a/mozilla/layout/xul/base/src/grid/nsGrid.cpp b/mozilla/layout/xul/base/src/grid/nsGrid.cpp
index b42b51e8a86..0a4369cb50f 100644
--- a/mozilla/layout/xul/base/src/grid/nsGrid.cpp
+++ b/mozilla/layout/xul/base/src/grid/nsGrid.cpp
@@ -935,7 +935,7 @@ nsGrid::GetPrefRowHeight(nsBoxLayoutState& aState, PRInt32 aIndex, PRBool aIsHor
      nsSize size(0,0);
      if (box) 
      {
-       box->GetPrefSize(aState, size);
+       size = box->GetPrefSize(aState);
        nsBox::AddMargin(box, size);
        nsStackLayout::AddOffset(aState, box, size);
      }
@@ -1009,7 +1009,7 @@ nsGrid::GetMinRowHeight(nsBoxLayoutState& aState, PRInt32 aIndex, PRBool aIsHori
   {
      nsSize size(0,0);
      if (box) {
-       box->GetPrefSize(aState, size);
+       size = box->GetPrefSize(aState);
        nsBox::AddMargin(box, size);
        nsStackLayout::AddOffset(aState, box, size);
      }
@@ -1085,7 +1085,7 @@ nsGrid::GetMaxRowHeight(nsBoxLayoutState& aState, PRInt32 aIndex, PRBool aIsHori
   {
      nsSize size(NS_INTRINSICSIZE,NS_INTRINSICSIZE);
      if (box) {
-       box->GetPrefSize(aState, size);
+       size = box->GetPrefSize(aState);
        nsBox::AddMargin(box, size);
        nsStackLayout::AddOffset(aState, box, size);
      }
diff --git a/mozilla/layout/xul/base/src/grid/nsGridCell.cpp b/mozilla/layout/xul/base/src/grid/nsGridCell.cpp
index a1d885df504..d5e2bd41e72 100644
--- a/mozilla/layout/xul/base/src/grid/nsGridCell.cpp
+++ b/mozilla/layout/xul/base/src/grid/nsGridCell.cpp
@@ -67,10 +67,9 @@ nsGridCell::GetPrefSize(nsBoxLayoutState& aState)
   // we are as wide as the widest child plus its left offset
   // we are tall as the tallest child plus its top offset
 
-  nsSize pref(0,0);
-
   if (mBoxInColumn) {
-    mBoxInColumn->GetPrefSize(aState, pref);      
+    nsSize pref = mBoxInColumn->GetPrefSize(aState);
+
     nsBox::AddMargin(mBoxInColumn, pref);
     nsStackLayout::AddOffset(aState, mBoxInColumn, pref);
 
@@ -78,7 +77,7 @@ nsGridCell::GetPrefSize(nsBoxLayoutState& aState)
   }
 
   if (mBoxInRow) {
-    mBoxInRow->GetPrefSize(aState, pref);
+    nsSize pref = mBoxInRow->GetPrefSize(aState);
 
     nsBox::AddMargin(mBoxInRow, pref);
     nsStackLayout::AddOffset(aState, mBoxInRow, pref);
@@ -98,10 +97,8 @@ nsGridCell::GetMinSize(nsBoxLayoutState& aState)
   // we are as wide as the widest child plus its left offset
   // we are tall as the tallest child plus its top offset
 
-  nsSize min(0,0);
-
   if (mBoxInColumn) {
-    mBoxInColumn->GetMinSize(aState, min);      
+    nsSize min = mBoxInColumn->GetMinSize(aState);
 
     nsBox::AddMargin(mBoxInColumn, min);
     nsStackLayout::AddOffset(aState, mBoxInColumn, min);
@@ -110,7 +107,7 @@ nsGridCell::GetMinSize(nsBoxLayoutState& aState)
   }
 
   if (mBoxInRow) {
-    mBoxInRow->GetMinSize(aState, min);
+    nsSize min = mBoxInRow->GetMinSize(aState);
 
     nsBox::AddMargin(mBoxInRow, min);
     nsStackLayout::AddOffset(aState, mBoxInRow, min);
@@ -130,10 +127,8 @@ nsGridCell::GetMaxSize(nsBoxLayoutState& aState)
   // we are as wide as the smallest child plus its left offset
   // we are tall as the shortest child plus its top offset
 
-  nsSize max(NS_INTRINSICSIZE,NS_INTRINSICSIZE);
-
   if (mBoxInColumn) {
-    mBoxInColumn->GetMaxSize(aState, max);      
+    nsSize max = mBoxInColumn->GetMaxSize(aState);
  
     nsBox::AddMargin(mBoxInColumn, max);
     nsStackLayout::AddOffset(aState, mBoxInColumn, max);
@@ -142,7 +137,7 @@ nsGridCell::GetMaxSize(nsBoxLayoutState& aState)
   }
 
   if (mBoxInRow) {
-    mBoxInRow->GetMaxSize(aState, max);
+    nsSize max = mBoxInRow->GetMaxSize(aState);
 
     nsBox::AddMargin(mBoxInRow, max);
     nsStackLayout::AddOffset(aState, mBoxInRow, max);
diff --git a/mozilla/layout/xul/base/src/nsBox.cpp b/mozilla/layout/xul/base/src/nsBox.cpp
index 73cd09f66ae..ea727be2652 100644
--- a/mozilla/layout/xul/base/src/nsBox.cpp
+++ b/mozilla/layout/xul/base/src/nsBox.cpp
@@ -517,47 +517,41 @@ nsBox::GetLayoutManager(nsIBoxLayout** aLayout)
 }
 
 
-NS_IMETHODIMP
-nsBox::GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsBox::GetPrefSize(nsBoxLayoutState& aState)
 {
-  DISPLAY_PREF_SIZE(this, aSize);
-  aSize.width = 0;
-  aSize.height = 0;
+  nsSize pref(0,0);
+  DISPLAY_PREF_SIZE(this, pref);
 
   PRBool collapsed = PR_FALSE;
   IsCollapsed(aState, collapsed);
   if (collapsed)
-    return NS_OK;
+    return pref;
 
-  AddBorderAndPadding(aSize);
-  AddInset(aSize);
-  nsIBox::AddCSSPrefSize(aState, this, aSize);
+  AddBorderAndPadding(pref);
+  AddInset(pref);
+  nsIBox::AddCSSPrefSize(aState, this, pref);
 
-  nsSize minSize(0, 0), maxSize(0, 0);
-  GetMinSize(aState, minSize);
-  GetMaxSize(aState, maxSize);
+  BoundsCheck(GetMinSize(aState), pref, GetMaxSize(aState));
 
-  BoundsCheck(minSize, aSize, maxSize);
-
-  return NS_OK;
+  return pref;
 }
 
-NS_IMETHODIMP
-nsBox::GetMinSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsBox::GetMinSize(nsBoxLayoutState& aState)
 {
-  DISPLAY_MIN_SIZE(this, aSize);
-  aSize.width = 0;
-  aSize.height = 0;
+  nsSize min(0,0);
+  DISPLAY_MIN_SIZE(this, min);
 
   PRBool collapsed = PR_FALSE;
   IsCollapsed(aState, collapsed);
   if (collapsed)
-    return NS_OK;
+    return min;
 
-  AddBorderAndPadding(aSize);
-  AddInset(aSize);
-  nsIBox::AddCSSMinSize(aState, this, aSize);
-  return NS_OK;
+  AddBorderAndPadding(min);
+  AddInset(min);
+  nsIBox::AddCSSMinSize(aState, this, min);
+  return min;
 }
 
 nsSize
@@ -566,22 +560,21 @@ nsBox::GetMinSizeForScrollArea(nsBoxLayoutState& aBoxLayoutState)
   return nsSize(0, 0);
 }
 
-NS_IMETHODIMP
-nsBox::GetMaxSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsBox::GetMaxSize(nsBoxLayoutState& aState)
 {
-  DISPLAY_MAX_SIZE(this, aSize);
-  aSize.width = NS_INTRINSICSIZE;
-  aSize.height = NS_INTRINSICSIZE;
+  nsSize max(NS_INTRINSICSIZE, NS_INTRINSICSIZE);
+  DISPLAY_MAX_SIZE(this, max);
 
   PRBool collapsed = PR_FALSE;
   IsCollapsed(aState, collapsed);
   if (collapsed)
-    return NS_OK;
+    return max;
 
-  AddBorderAndPadding(aSize);
-  AddInset(aSize);
-  nsIBox::AddCSSMaxSize(aState, this, aSize);
-  return NS_OK;
+  AddBorderAndPadding(max);
+  AddInset(max);
+  nsIBox::AddCSSMaxSize(aState, this, max);
+  return max;
 }
 
 NS_IMETHODIMP
@@ -613,10 +606,8 @@ nsBox::GetAscent(nsBoxLayoutState& aState, nscoord& aAscent)
   if (collapsed)
     return NS_OK;
 
-  nsSize size(0,0);
-  nsresult rv = GetPrefSize(aState, size);
-  aAscent = size.height;
-  return rv;
+  aAscent = GetPrefSize(aState).height;
+  return NS_OK;
 }
 
 NS_IMETHODIMP
diff --git a/mozilla/layout/xul/base/src/nsBox.h b/mozilla/layout/xul/base/src/nsBox.h
index 9db5ffcc2dc..7d184934bfb 100644
--- a/mozilla/layout/xul/base/src/nsBox.h
+++ b/mozilla/layout/xul/base/src/nsBox.h
@@ -57,9 +57,9 @@ public:
 
   static void Shutdown();
 
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMaxSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMaxSize(nsBoxLayoutState& aBoxLayoutState);
   NS_IMETHOD GetFlex(nsBoxLayoutState& aBoxLayoutState, nscoord& aFlex);
   NS_IMETHOD GetAscent(nsBoxLayoutState& aBoxLayoutState, nscoord& aAscent);
 
diff --git a/mozilla/layout/xul/base/src/nsBoxFrame.cpp b/mozilla/layout/xul/base/src/nsBoxFrame.cpp
index c2615a73a4b..dfee1b8a66c 100644
--- a/mozilla/layout/xul/base/src/nsBoxFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsBoxFrame.cpp
@@ -671,8 +671,7 @@ nsBoxFrame::GetMinWidth(nsIRenderingContext *aRenderingContext)
   DISPLAY_MIN_WIDTH(this, result);
 
   nsBoxLayoutState state(GetPresContext(), aRenderingContext);
-  nsSize minSize(0,0);
-  GetMinSize(state, minSize);
+  nsSize minSize = GetMinSize(state);
 
   // GetMinSize returns border-box width, and we want to return content
   // width.  Since Reflow uses the reflow state's border and padding, we
@@ -693,8 +692,7 @@ nsBoxFrame::GetPrefWidth(nsIRenderingContext *aRenderingContext)
   DISPLAY_PREF_WIDTH(this, result);
 
   nsBoxLayoutState state(GetPresContext(), aRenderingContext);
-  nsSize prefSize(0,0);
-  GetPrefSize(state, prefSize);
+  nsSize prefSize = GetPrefSize(state);
 
   // GetPrefSize returns border-box width, and we want to return content
   // width.  Since Reflow uses the reflow state's border and padding, we
@@ -748,16 +746,12 @@ nsBoxFrame::Reflow(nsPresContext*          aPresContext,
 
   nsSize prefSize(0,0);
 
-  // if we are told to layout intrinic then get our preferred size.
+  // if we are told to layout intrinsic then get our preferred size.
   NS_ASSERTION(computedSize.width != NS_INTRINSICSIZE,
                "computed width should always be computed");
   if (computedSize.height == NS_INTRINSICSIZE) {
-     nsSize minSize(0,0);
-     nsSize maxSize(0,0);
-     GetPrefSize(state, prefSize);
-     GetMinSize(state,  minSize);
-     GetMaxSize(state,  maxSize);
-     BoundsCheck(minSize, prefSize, maxSize);
+    prefSize = GetPrefSize(state);
+    BoundsCheck(GetMinSize(state), prefSize, GetMaxSize(state));
   }
 
   // get our desiredSize
@@ -830,52 +824,39 @@ nsBoxFrame::Reflow(nsPresContext*          aPresContext,
   return NS_OK;
 }
 
-NS_IMETHODIMP
-nsBoxFrame::GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)
+nsSize
+nsBoxFrame::GetPrefSize(nsBoxLayoutState& aBoxLayoutState)
 {
-  DISPLAY_PREF_SIZE(this, aSize);
+  nsSize size(0,0);
+  DISPLAY_PREF_SIZE(this, size);
   if (!DoesNeedRecalc(mPrefSize)) {
-     aSize = mPrefSize;
-     return NS_OK;
+     size = mPrefSize;
+     return size;
   }
 
 #ifdef DEBUG_LAYOUT
   PropagateDebug(aBoxLayoutState);
 #endif
 
-  nsresult rv = NS_OK;
-  aSize.width = 0;
-  aSize.height = 0;
-
   PRBool collapsed = PR_FALSE;
   IsCollapsed(aBoxLayoutState, collapsed);
-  if (collapsed) {
-    return NS_OK;
-  }
+  if (collapsed)
+    return size;
 
   // if the size was not completely redefined in CSS then ask our children
-  if (!nsIBox::AddCSSPrefSize(aBoxLayoutState, this, aSize))
+  if (!nsIBox::AddCSSPrefSize(aBoxLayoutState, this, size))
   {
-    aSize.width = 0;
-    aSize.height = 0;
-
     if (mLayoutManager) {
-      rv = mLayoutManager->GetPrefSize(this, aBoxLayoutState, aSize);
-      nsIBox::AddCSSPrefSize(aBoxLayoutState, this, aSize);
+      mLayoutManager->GetPrefSize(this, aBoxLayoutState, size);
+      nsIBox::AddCSSPrefSize(aBoxLayoutState, this, size);
     } else
-      rv = nsBox::GetPrefSize(aBoxLayoutState, aSize);
+      size = nsBox::GetPrefSize(aBoxLayoutState);
   }
 
-  nsSize minSize(0,0);
-  nsSize maxSize(0,0);
-  GetMinSize(aBoxLayoutState, minSize);
-  GetMaxSize(aBoxLayoutState, maxSize);
-
-  BoundsCheck(minSize, aSize, maxSize);
-
-  mPrefSize = aSize;
+  BoundsCheck(GetMinSize(aBoxLayoutState), size, GetMaxSize(aBoxLayoutState));
+  mPrefSize = size;
  
-  return rv;
+  return size;
 }
 
 NS_IMETHODIMP
@@ -908,86 +889,74 @@ nsBoxFrame::GetAscent(nsBoxLayoutState& aBoxLayoutState, nscoord& aAscent)
   return rv;
 }
 
-NS_IMETHODIMP
-nsBoxFrame::GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)
+nsSize
+nsBoxFrame::GetMinSize(nsBoxLayoutState& aBoxLayoutState)
 {
-  DISPLAY_MIN_SIZE(this, aSize);
+  nsSize size(0,0);
+  DISPLAY_MIN_SIZE(this, size);
   if (!DoesNeedRecalc(mMinSize)) {
-     aSize = mMinSize;
-     return NS_OK;
+    size = mMinSize;
+    return size;
   }
 
 #ifdef DEBUG_LAYOUT
   PropagateDebug(aBoxLayoutState);
 #endif
 
-  nsresult rv = NS_OK;
-
-  aSize.SizeTo(0, 0);
-
   PRBool collapsed = PR_FALSE;
   IsCollapsed(aBoxLayoutState, collapsed);
   if (collapsed)
-    return NS_OK;
+    return size;
 
   // if the size was not completely redefined in CSS then ask our children
-  if (!nsIBox::AddCSSMinSize(aBoxLayoutState, this, aSize))
+  if (!nsIBox::AddCSSMinSize(aBoxLayoutState, this, size))
   {
-    aSize.width = 0;
-    aSize.height = 0;
-
     if (mLayoutManager) {
-      rv = mLayoutManager->GetMinSize(this, aBoxLayoutState, aSize);
-      nsIBox::AddCSSMinSize(aBoxLayoutState, this, aSize);
+      mLayoutManager->GetMinSize(this, aBoxLayoutState, size);
+      nsIBox::AddCSSMinSize(aBoxLayoutState, this, size);
     } else {
-      rv = nsBox::GetMinSize(aBoxLayoutState, aSize);
+      size = nsBox::GetMinSize(aBoxLayoutState);
     }
   }
   
-  mMinSize = aSize;
+  mMinSize = size;
 
-  return rv;
+  return size;
 }
 
-NS_IMETHODIMP
-nsBoxFrame::GetMaxSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)
+nsSize
+nsBoxFrame::GetMaxSize(nsBoxLayoutState& aBoxLayoutState)
 {
-  DISPLAY_MAX_SIZE(this, aSize);
+  nsSize size(NS_INTRINSICSIZE, NS_INTRINSICSIZE);
+  DISPLAY_MAX_SIZE(this, size);
   if (!DoesNeedRecalc(mMaxSize)) {
-     aSize = mMaxSize;
-     return NS_OK;
+    size = mMaxSize;
+    return size;
   }
 
 #ifdef DEBUG_LAYOUT
   PropagateDebug(aBoxLayoutState);
 #endif
 
-  nsresult rv = NS_OK;
-
-  aSize.SizeTo(NS_INTRINSICSIZE, NS_INTRINSICSIZE);
-
   PRBool collapsed = PR_FALSE;
   IsCollapsed(aBoxLayoutState, collapsed);
   if (collapsed)
-    return NS_OK;
+    return size;
 
   // if the size was not completely redefined in CSS then ask our children
-  if (!nsIBox::AddCSSMaxSize(aBoxLayoutState, this, aSize))
+  if (!nsIBox::AddCSSMaxSize(aBoxLayoutState, this, size))
   {
-    aSize.width = NS_INTRINSICSIZE;
-    aSize.height = NS_INTRINSICSIZE;
-
     if (mLayoutManager) {
-      rv = mLayoutManager->GetMaxSize(this, aBoxLayoutState, aSize);
-      nsIBox::AddCSSMaxSize(aBoxLayoutState, this, aSize);
+      mLayoutManager->GetMaxSize(this, aBoxLayoutState, size);
+      nsIBox::AddCSSMaxSize(aBoxLayoutState, this, size);
     } else {
-      rv = nsBox::GetMaxSize(aBoxLayoutState, aSize);
+      size = nsBox::GetMaxSize(aBoxLayoutState);
     }
   }
 
-  mMaxSize = aSize;
+  mMaxSize = size;
 
-  return rv;
+  return size;
 }
 
 NS_IMETHODIMP
@@ -1889,9 +1858,6 @@ nsBoxFrame::DisplayDebugInfoFor(nsIBox*  aBox,
                     nsSize maxSizeCSS (NS_INTRINSICSIZE, NS_INTRINSICSIZE);
                     nscoord flexCSS = NS_INTRINSICSIZE;
 
-                    nsSize prefSize(0, 0);
-                    nsSize minSize (0, 0);
-                    nsSize maxSize (NS_INTRINSICSIZE, NS_INTRINSICSIZE);
                     nscoord flexSize = 0;
                     nscoord ascentSize = 0;
 
@@ -1901,9 +1867,9 @@ nsBoxFrame::DisplayDebugInfoFor(nsIBox*  aBox,
                     nsIBox::AddCSSMaxSize (state, child, maxSizeCSS);
                     nsIBox::AddCSSFlex    (state, child, flexCSS);
 
-                    child->GetPrefSize(state, prefSize);
-                    child->GetMinSize(state, minSize);
-                    child->GetMaxSize(state, maxSize);
+                    nsSize prefSize = child->GetPrefSize(state);
+                    nsSize minSize = child->GetMinSize(state);
+                    nsSize maxSize = child->GetMaxSize(state);
                     child->GetFlex(state, flexSize);
                     child->GetAscent(state, ascentSize);
 
diff --git a/mozilla/layout/xul/base/src/nsBoxFrame.h b/mozilla/layout/xul/base/src/nsBoxFrame.h
index a7b86b658df..6a49b032b1b 100644
--- a/mozilla/layout/xul/base/src/nsBoxFrame.h
+++ b/mozilla/layout/xul/base/src/nsBoxFrame.h
@@ -100,9 +100,9 @@ public:
   NS_IMETHOD RelayoutChildAtOrdinal(nsBoxLayoutState& aState, nsIBox* aChild);
   NS_IMETHOD GetIndexOf(nsIBox* aChild, PRInt32* aIndex);
 
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMaxSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMaxSize(nsBoxLayoutState& aBoxLayoutState);
   NS_IMETHOD GetFlex(nsBoxLayoutState& aBoxLayoutState, nscoord& aFlex);
   NS_IMETHOD GetAscent(nsBoxLayoutState& aBoxLayoutState, nscoord& aAscent);
 #ifdef DEBUG_LAYOUT
diff --git a/mozilla/layout/xul/base/src/nsImageBoxFrame.cpp b/mozilla/layout/xul/base/src/nsImageBoxFrame.cpp
index 1327ff38761..db4e3001df2 100644
--- a/mozilla/layout/xul/base/src/nsImageBoxFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsImageBoxFrame.cpp
@@ -461,50 +461,43 @@ nsImageBoxFrame::GetImageSize()
 /**
  * Ok return our dimensions
  */
-NS_IMETHODIMP
-nsImageBoxFrame::GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsImageBoxFrame::GetPrefSize(nsBoxLayoutState& aState)
 {
-  DISPLAY_PREF_SIZE(this, aSize);
-  if (DoesNeedRecalc(mImageSize)) {
+  nsSize size(0,0);
+  DISPLAY_PREF_SIZE(this, size);
+  if (DoesNeedRecalc(mImageSize))
      GetImageSize();
-  }
 
   if (!mUseSrcAttr && (mSubRect.width > 0 || mSubRect.height > 0))
-    aSize = nsSize(mSubRect.width, mSubRect.height);
+    size = nsSize(mSubRect.width, mSubRect.height);
   else
-    aSize = mImageSize;
-  AddBorderAndPadding(aSize);
-  AddInset(aSize);
-  nsIBox::AddCSSPrefSize(aState, this, aSize);
+    size = mImageSize;
+  AddBorderAndPadding(size);
+  AddInset(size);
+  nsIBox::AddCSSPrefSize(aState, this, size);
 
-  nsSize minSize(0,0);
-  nsSize maxSize(0,0);
-  GetMinSize(aState, minSize);
-  GetMaxSize(aState, maxSize);
+  BoundsCheck(GetMinSize(aState), size, GetMaxSize(aState));
 
-  BoundsCheck(minSize, aSize, maxSize);
-
-  return NS_OK;
+  return size;
 }
 
-NS_IMETHODIMP
-nsImageBoxFrame::GetMinSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsImageBoxFrame::GetMinSize(nsBoxLayoutState& aState)
 {
-  DISPLAY_MIN_SIZE(this, aSize);
   // An image can always scale down to (0,0).
-  aSize.width = aSize.height = 0;
-  AddBorderAndPadding(aSize);
-  AddInset(aSize);
-  nsIBox::AddCSSMinSize(aState, this, aSize);
-  return NS_OK;
+  nsSize size(0,0);
+  DISPLAY_MIN_SIZE(this, size);
+  AddBorderAndPadding(size);
+  AddInset(size);
+  nsIBox::AddCSSMinSize(aState, this, size);
+  return size;
 }
 
 NS_IMETHODIMP
 nsImageBoxFrame::GetAscent(nsBoxLayoutState& aState, nscoord& aCoord)
 {
-  nsSize size(0,0);
-  GetPrefSize(aState, size);
-  aCoord = size.height;
+  aCoord = GetPrefSize(aState).height;
   return NS_OK;
 }
 
diff --git a/mozilla/layout/xul/base/src/nsImageBoxFrame.h b/mozilla/layout/xul/base/src/nsImageBoxFrame.h
index 94d9126b11c..5a2119dfe37 100644
--- a/mozilla/layout/xul/base/src/nsImageBoxFrame.h
+++ b/mozilla/layout/xul/base/src/nsImageBoxFrame.h
@@ -73,8 +73,8 @@ class nsImageBoxFrame : public nsLeafBoxFrame
 public:
 
   // nsIBox
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState);
   NS_IMETHOD GetAscent(nsBoxLayoutState& aBoxLayoutState, nscoord& aAscent);
   virtual void MarkIntrinsicWidthsDirty();
 
diff --git a/mozilla/layout/xul/base/src/nsLeafBoxFrame.cpp b/mozilla/layout/xul/base/src/nsLeafBoxFrame.cpp
index f71d2cc4a7d..5086a189887 100644
--- a/mozilla/layout/xul/base/src/nsLeafBoxFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsLeafBoxFrame.cpp
@@ -197,8 +197,7 @@ nsLeafBoxFrame::GetMinWidth(nsIRenderingContext *aRenderingContext)
   nscoord result;
   DISPLAY_MIN_WIDTH(this, result);
   nsBoxLayoutState state(GetPresContext(), aRenderingContext);
-  nsSize minSize(0,0);
-  GetMinSize(state, minSize);
+  nsSize minSize = GetMinSize(state);
 
   // GetMinSize returns border-box width, and we want to return content
   // width.  Since Reflow uses the reflow state's border and padding, we
@@ -218,8 +217,7 @@ nsLeafBoxFrame::GetPrefWidth(nsIRenderingContext *aRenderingContext)
   nscoord result;
   DISPLAY_PREF_WIDTH(this, result);
   nsBoxLayoutState state(GetPresContext(), aRenderingContext);
-  nsSize prefSize(0,0);
-  GetPrefSize(state, prefSize);
+  nsSize prefSize = GetPrefSize(state);
 
   // GetPrefSize returns border-box width, and we want to return content
   // width.  Since Reflow uses the reflow state's border and padding, we
@@ -297,8 +295,7 @@ nsLeafBoxFrame::Reflow(nsPresContext*   aPresContext,
 
   // this happens sometimes. So lets handle it gracefully.
   if (aReflowState.mComputedHeight == 0) {
-    nsSize minSize(0,0);
-    GetMinSize(state, minSize);
+    nsSize minSize = GetMinSize(state);
     computedSize.height = minSize.height - m.top - m.bottom;
   }
 
@@ -306,12 +303,8 @@ nsLeafBoxFrame::Reflow(nsPresContext*   aPresContext,
 
   // if we are told to layout intrinic then get our preferred size.
   if (computedSize.width == NS_INTRINSICSIZE || computedSize.height == NS_INTRINSICSIZE) {
-     nsSize minSize(0,0);
-     nsSize maxSize(0,0);
-     GetPrefSize(state, prefSize);
-     GetMinSize(state,  minSize);
-     GetMaxSize(state,  maxSize);
-     BoundsCheck(minSize, prefSize, maxSize);
+     prefSize = GetPrefSize(state);
+     BoundsCheck(GetMinSize(state), prefSize, GetMaxSize(state));
   }
 
   // get our desiredSize
@@ -418,22 +411,22 @@ nsLeafBoxFrame::CharacterDataChanged(nsPresContext* aPresContext,
   return nsLeafFrame::CharacterDataChanged(aPresContext, aChild, aAppend);
 }
 
-NS_IMETHODIMP
-nsLeafBoxFrame::GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize)
+/* virtual */ nsSize
+nsLeafBoxFrame::GetPrefSize(nsBoxLayoutState& aState)
 {
-    return nsBox::GetPrefSize(aState, aSize);
+    return nsBox::GetPrefSize(aState);
 }
 
-NS_IMETHODIMP
-nsLeafBoxFrame::GetMinSize(nsBoxLayoutState& aState, nsSize& aSize)
+/* virtual */ nsSize
+nsLeafBoxFrame::GetMinSize(nsBoxLayoutState& aState)
 {
-    return nsBox::GetMinSize(aState, aSize);
+    return nsBox::GetMinSize(aState);
 }
 
-NS_IMETHODIMP
-nsLeafBoxFrame::GetMaxSize(nsBoxLayoutState& aState, nsSize& aSize)
+/* virtual */ nsSize
+nsLeafBoxFrame::GetMaxSize(nsBoxLayoutState& aState)
 {
-    return nsBox::GetMaxSize(aState, aSize);
+    return nsBox::GetMaxSize(aState);
 }
 
 NS_IMETHODIMP
diff --git a/mozilla/layout/xul/base/src/nsLeafBoxFrame.h b/mozilla/layout/xul/base/src/nsLeafBoxFrame.h
index 0167d8e44b2..7b258832500 100644
--- a/mozilla/layout/xul/base/src/nsLeafBoxFrame.h
+++ b/mozilla/layout/xul/base/src/nsLeafBoxFrame.h
@@ -52,9 +52,9 @@ public:
   NS_IMETHOD_(nsrefcnt) AddRef(void);
   NS_IMETHOD_(nsrefcnt) Release(void);
 
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize);
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aState, nsSize& aSize);
-  NS_IMETHOD GetMaxSize(nsBoxLayoutState& aState, nsSize& aSize);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aState);
+  virtual nsSize GetMinSize(nsBoxLayoutState& aState);
+  virtual nsSize GetMaxSize(nsBoxLayoutState& aState);
   NS_IMETHOD GetFlex(nsBoxLayoutState& aState, nscoord& aFlex);
   NS_IMETHOD GetAscent(nsBoxLayoutState& aState, nscoord& aAscent);
 
diff --git a/mozilla/layout/xul/base/src/nsListBoxBodyFrame.cpp b/mozilla/layout/xul/base/src/nsListBoxBodyFrame.cpp
index 7f0181e65af..00d08f85374 100644
--- a/mozilla/layout/xul/base/src/nsListBoxBodyFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsListBoxBodyFrame.cpp
@@ -371,7 +371,7 @@ nsListBoxBodyFrame::GetMinSizeForScrollArea(nsBoxLayoutState& aBoxLayoutState)
   nsSize result(0, 0);
   if (nsContentUtils::HasNonEmptyAttr(GetContent(), kNameSpaceID_None,
                                       nsGkAtoms::sizemode)) {
-    GetPrefSize(aBoxLayoutState, result);
+    result = GetPrefSize(aBoxLayoutState);
     result.height = 0;
     nsIScrollableFrame* scrollFrame = nsLayoutUtils::GetScrollableFrameFor(this);
     if (scrollFrame &&
@@ -384,24 +384,24 @@ nsListBoxBodyFrame::GetMinSizeForScrollArea(nsBoxLayoutState& aBoxLayoutState)
   return result;
 }
 
-NS_IMETHODIMP
-nsListBoxBodyFrame::GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)
+nsSize
+nsListBoxBodyFrame::GetPrefSize(nsBoxLayoutState& aBoxLayoutState)
 {  
-  nsresult rv = nsBoxFrame::GetPrefSize(aBoxLayoutState, aSize);
+  nsSize pref = nsBoxFrame::GetPrefSize(aBoxLayoutState);
 
   PRInt32 size = GetFixedRowSize();
   nsIBox* box = nsnull;
   GetChildBox(&box);
   if (size > -1)
-    aSize.height = size*GetRowHeightTwips();
+    pref.height = size*GetRowHeightTwips();
    
   nsIScrollableFrame* scrollFrame = nsLayoutUtils::GetScrollableFrameFor(this);
   if (scrollFrame &&
       scrollFrame->GetScrollbarStyles().mVertical == NS_STYLE_OVERFLOW_AUTO) {
     nsMargin scrollbars = scrollFrame->GetDesiredScrollbarSizes(&aBoxLayoutState);
-    aSize.width += scrollbars.left + scrollbars.right;
+    pref.width += scrollbars.left + scrollbars.right;
   }
-  return rv;
+  return pref;
 }
 
 ///////////// nsIScrollbarMediator ///////////////
diff --git a/mozilla/layout/xul/base/src/nsListBoxBodyFrame.h b/mozilla/layout/xul/base/src/nsListBoxBodyFrame.h
index b0cdd95b35b..3c3e6816437 100644
--- a/mozilla/layout/xul/base/src/nsListBoxBodyFrame.h
+++ b/mozilla/layout/xul/base/src/nsListBoxBodyFrame.h
@@ -93,7 +93,7 @@ public:
   virtual void MarkIntrinsicWidthsDirty();
 
   virtual nsSize GetMinSizeForScrollArea(nsBoxLayoutState& aBoxLayoutState);
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState);
 
   // size calculation 
   PRInt32 GetRowCount();
diff --git a/mozilla/layout/xul/base/src/nsListBoxLayout.cpp b/mozilla/layout/xul/base/src/nsListBoxLayout.cpp
index 342326643ba..35ec1dd1b73 100644
--- a/mozilla/layout/xul/base/src/nsListBoxLayout.cpp
+++ b/mozilla/layout/xul/base/src/nsListBoxLayout.cpp
@@ -211,8 +211,7 @@ nsListBoxLayout::LayoutInternal(nsIBox* aBox, nsBoxLayoutState& aState)
       childRect.y = yOffset;
       childRect.width = clientRect.width;
       
-      nsSize size;
-      box->GetPrefSize(aState, size);
+      nsSize size = box->GetPrefSize(aState);
       body->SetRowHeight(size.height);
       
       childRect.height = rowHeight;
diff --git a/mozilla/layout/xul/base/src/nsListItemFrame.cpp b/mozilla/layout/xul/base/src/nsListItemFrame.cpp
index f5313d65258..f2922bc106c 100644
--- a/mozilla/layout/xul/base/src/nsListItemFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsListItemFrame.cpp
@@ -71,17 +71,16 @@ nsListItemFrame::~nsListItemFrame()
 {
 }
 
-nsresult
-nsListItemFrame::GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsListItemFrame::GetPrefSize(nsBoxLayoutState& aState)
 {
-  DISPLAY_PREF_SIZE(this, aSize);
-  nsresult rv = nsBoxFrame::GetPrefSize(aState, aSize);
-  if (NS_FAILED(rv)) return rv;
+  nsSize size = nsBoxFrame::GetPrefSize(aState);  
+  DISPLAY_PREF_SIZE(this, size);
 
   // guarantee that our preferred height doesn't exceed the standard
   // listbox row height
-  aSize.height = PR_MAX(mRect.height, aSize.height);
-  return NS_OK;
+  size.height = PR_MAX(mRect.height, size.height);
+  return size;
 }
 
 NS_IMETHODIMP
diff --git a/mozilla/layout/xul/base/src/nsListItemFrame.h b/mozilla/layout/xul/base/src/nsListItemFrame.h
index 0dce9dcb884..ac972e05525 100644
--- a/mozilla/layout/xul/base/src/nsListItemFrame.h
+++ b/mozilla/layout/xul/base/src/nsListItemFrame.h
@@ -62,7 +62,7 @@ public:
                                          const nsDisplayListSet& aLists);
 
   // nsIBox
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aState);
   
 protected:
   nsListItemFrame(nsIPresShell* aPresShell,
diff --git a/mozilla/layout/xul/base/src/nsMenuFrame.cpp b/mozilla/layout/xul/base/src/nsMenuFrame.cpp
index 28110453d26..39a409e87ae 100644
--- a/mozilla/layout/xul/base/src/nsMenuFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsMenuFrame.cpp
@@ -1016,16 +1016,16 @@ nsMenuFrame::IsSizedToPopup(nsIContent* aContent, PRBool aRequireAlways)
   return sizeToPopup;
 }
 
-NS_IMETHODIMP
-nsMenuFrame::GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)
+nsSize
+nsMenuFrame::GetMinSize(nsBoxLayoutState& aBoxLayoutState)
 {
-  DISPLAY_MIN_SIZE(this, aSize);
-  nsresult rv = nsBoxFrame::GetMinSize(aBoxLayoutState, aSize);
+  nsSize size = nsBoxFrame::GetMinSize(aBoxLayoutState);
+  DISPLAY_MIN_SIZE(this, size);
 
   if (IsSizedToPopup(mContent, PR_TRUE))
-    SizeToPopup(aBoxLayoutState, aSize);
+    SizeToPopup(aBoxLayoutState, size);
 
-  return rv;
+  return size;
 }
 
 NS_IMETHODIMP
@@ -1046,13 +1046,9 @@ nsMenuFrame::DoLayout(nsBoxLayoutState& aState)
     NS_ASSERTION(popupChild->IsBoxFrame(), "popupChild is not box!!");
 
     // then get its preferred size
-    nsSize prefSize(0,0);
-    nsSize minSize(0,0);
-    nsSize maxSize(0,0);
-
-    popupChild->GetPrefSize(aState, prefSize);
-    popupChild->GetMinSize(aState, minSize);
-    popupChild->GetMaxSize(aState, maxSize);
+    nsSize prefSize = popupChild->GetPrefSize(aState);
+    nsSize minSize = popupChild->GetMinSize(aState); 
+    nsSize maxSize = popupChild->GetMaxSize(aState);
 
     BoundsCheck(minSize, prefSize, maxSize);
 
@@ -2004,7 +2000,7 @@ nsMenuFrame::SizeToPopup(nsBoxLayoutState& aState, nsSize& aSize)
 
       NS_ASSERTION(frame->IsBoxFrame(), "popupChild is not box!!");
 
-      frame->GetPrefSize(aState, tmpSize);
+      tmpSize = frame->GetPrefSize(aState);
       aSize.width = tmpSize.width;
       return PR_TRUE;
     }
@@ -2013,25 +2009,24 @@ nsMenuFrame::SizeToPopup(nsBoxLayoutState& aState, nsSize& aSize)
   return PR_FALSE;
 }
 
-NS_IMETHODIMP
-nsMenuFrame::GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsMenuFrame::GetPrefSize(nsBoxLayoutState& aState)
 {
-  DISPLAY_PREF_SIZE(this, aSize);
-  nsresult rv = nsBoxFrame::GetPrefSize(aState, aSize);
+  nsSize size = nsBoxFrame::GetPrefSize(aState);
+  DISPLAY_PREF_SIZE(this, size);
 
   // If we are using sizetopopup="always" then
   // nsBoxFrame will already have enforced the minimum size
   if (!IsSizedToPopup(mContent, PR_TRUE) &&
       IsSizedToPopup(mContent, PR_FALSE) &&
-      SizeToPopup(aState, aSize)) {
-    // We now need to ensure that aSize is within the min size - max size range.
-    nsSize minSize, maxSize;
-    nsBoxFrame::GetMinSize(aState, minSize);
-    GetMaxSize(aState, maxSize);
-    BoundsCheck(minSize, aSize, maxSize);
+      SizeToPopup(aState, size)) {
+    // We now need to ensure that size is within the min - max range.
+    nsSize minSize = nsBoxFrame::GetMinSize(aState);
+    nsSize maxSize = GetMaxSize(aState);
+    BoundsCheck(minSize, size, maxSize);
   }
 
-  return rv;
+  return size;
 }
 
 NS_IMETHODIMP
diff --git a/mozilla/layout/xul/base/src/nsMenuFrame.h b/mozilla/layout/xul/base/src/nsMenuFrame.h
index afbdd7a25ba..bf71e1358f1 100644
--- a/mozilla/layout/xul/base/src/nsMenuFrame.h
+++ b/mozilla/layout/xul/base/src/nsMenuFrame.h
@@ -109,8 +109,8 @@ public:
 
   // nsIBox
   NS_IMETHOD DoLayout(nsBoxLayoutState& aBoxLayoutState);
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
+  virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState);
 
   NS_IMETHOD Init(nsIContent*      aContent,
                   nsIFrame*        aParent,
diff --git a/mozilla/layout/xul/base/src/nsNativeScrollbarFrame.cpp b/mozilla/layout/xul/base/src/nsNativeScrollbarFrame.cpp
index 0a33ea22c2e..af018df38be 100644
--- a/mozilla/layout/xul/base/src/nsNativeScrollbarFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsNativeScrollbarFrame.cpp
@@ -252,29 +252,30 @@ nsNativeScrollbarFrame::AttributeChanged(PRInt32 aNameSpaceID,
 // Ask our native widget what dimensions it wants to be, convert them
 // back to twips, and tell gecko.
 //
-NS_IMETHODIMP
-nsNativeScrollbarFrame::GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsNativeScrollbarFrame::GetPrefSize(nsBoxLayoutState& aState)
 {
-  DISPLAY_PREF_SIZE(this, aSize);
+  nsSize size(0,0);
+  DISPLAY_PREF_SIZE(this, size);
   float p2t = 0.0;
   p2t = aState.PresContext()->PixelsToTwips();
   
   PRInt32 narrowDimension = 0;
   nsCOMPtr<nsINativeScrollbar> native ( do_QueryInterface(mScrollbar) );
-  if ( !native ) return NS_ERROR_FAILURE;  
+  if ( !native ) return size;
   native->GetNarrowSize(&narrowDimension);
   
   if ( IsVertical() )
-    aSize.width = nscoord(narrowDimension * p2t);
+    size.width = nscoord(narrowDimension * p2t);
   else
-    aSize.height = nscoord(narrowDimension * p2t);
+    size.height = nscoord(narrowDimension * p2t);
   
   // By now, we have both the content node for the scrollbar and the associated
   // scrollbar mediator (for outliner, if applicable). Hook up the scrollbar to
   // gecko
   Hookup();
     
-  return NS_OK;
+  return size;
 }
 
 
diff --git a/mozilla/layout/xul/base/src/nsNativeScrollbarFrame.h b/mozilla/layout/xul/base/src/nsNativeScrollbarFrame.h
index 3ea3e1bf964..2d872cc8de2 100644
--- a/mozilla/layout/xul/base/src/nsNativeScrollbarFrame.h
+++ b/mozilla/layout/xul/base/src/nsNativeScrollbarFrame.h
@@ -87,7 +87,7 @@ public:
                     const nsHTMLReflowState& aReflowState,
                     nsReflowStatus&          aStatus);
 
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aState);
 
   virtual void Destroy();
 
diff --git a/mozilla/layout/xul/base/src/nsPopupSetFrame.cpp b/mozilla/layout/xul/base/src/nsPopupSetFrame.cpp
index be6c01bf733..5e0fae22926 100644
--- a/mozilla/layout/xul/base/src/nsPopupSetFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsPopupSetFrame.cpp
@@ -249,13 +249,9 @@ nsPopupSetFrame::DoLayout(nsBoxLayoutState& aState)
       NS_ASSERTION(popupChild->IsBoxFrame(), "popupChild is not box!!");
 
       // then get its preferred size
-      nsSize prefSize(0,0);
-      nsSize minSize(0,0);
-      nsSize maxSize(0,0);
-
-      popupChild->GetPrefSize(aState, prefSize);
-      popupChild->GetMinSize(aState, minSize);
-      popupChild->GetMaxSize(aState, maxSize);
+      nsSize prefSize = popupChild->GetPrefSize(aState);
+      nsSize minSize = popupChild->GetMinSize(aState);
+      nsSize maxSize = popupChild->GetMaxSize(aState);
 
       BoundsCheck(minSize, prefSize, maxSize);
 
diff --git a/mozilla/layout/xul/base/src/nsSliderFrame.cpp b/mozilla/layout/xul/base/src/nsSliderFrame.cpp
index 76228e8d940..6cd9608ab29 100644
--- a/mozilla/layout/xul/base/src/nsSliderFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsSliderFrame.cpp
@@ -349,8 +349,7 @@ nsSliderFrame::DoLayout(nsBoxLayoutState& aState)
   PRBool isHorizontal = IsHorizontal();
 
   // get the thumb's pref size
-  nsSize thumbSize(0,0);
-  thumbBox->GetPrefSize(aState, thumbSize);
+  nsSize thumbSize = thumbBox->GetPrefSize(aState);
 
   if (isHorizontal)
     thumbSize.height = clientRect.height;
@@ -1011,27 +1010,27 @@ nsSliderFrame::Destroy()
   nsBoxFrame::Destroy();
 }
 
-NS_IMETHODIMP
-nsSliderFrame::GetPrefSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsSliderFrame::GetPrefSize(nsBoxLayoutState& aState)
 {
   EnsureOrient();
-  return nsBoxFrame::GetPrefSize(aState, aSize);
+  return nsBoxFrame::GetPrefSize(aState);
 }
 
-NS_IMETHODIMP
-nsSliderFrame::GetMinSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsSliderFrame::GetMinSize(nsBoxLayoutState& aState)
 {
   EnsureOrient();
 
   // our min size is just our borders and padding
-  return nsBox::GetMinSize(aState, aSize);
+  return nsBox::GetMinSize(aState);
 }
 
-NS_IMETHODIMP
-nsSliderFrame::GetMaxSize(nsBoxLayoutState& aState, nsSize& aSize)
+nsSize
+nsSliderFrame::GetMaxSize(nsBoxLayoutState& aState)
 {
   EnsureOrient();
-  return nsBoxFrame::GetMaxSize(aState, aSize);
+  return nsBoxFrame::GetMaxSize(aState);
 }
 
 void
diff --git a/mozilla/layout/xul/base/src/nsSliderFrame.h b/mozilla/layout/xul/base/src/nsSliderFrame.h
index d0fb0e59fdd..2eb8329d78c 100644
--- a/mozilla/layout/xul/base/src/nsSliderFrame.h
+++ b/mozilla/layout/xul/base/src/nsSliderFrame.h
@@ -134,9 +134,9 @@ public:
 #endif
 
   // nsIBox
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMaxSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMaxSize(nsBoxLayoutState& aBoxLayoutState);
   NS_IMETHOD DoLayout(nsBoxLayoutState& aBoxLayoutState);
 
   // nsIFrame overrides
diff --git a/mozilla/layout/xul/base/src/nsSplitterFrame.cpp b/mozilla/layout/xul/base/src/nsSplitterFrame.cpp
index b5d553b3458..c73a5103fcf 100644
--- a/mozilla/layout/xul/base/src/nsSplitterFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsSplitterFrame.cpp
@@ -775,20 +775,16 @@ nsSplitterFrameInner::MouseDown(nsIDOMEvent* aMouseEvent)
 
     // skip over any splitters
     if (atom != nsGkAtoms::splitter) { 
-        nsSize prefSize(0,0);
-        nsSize minSize(0,0);
-        nsSize maxSize(0,0);
-        nscoord flex = 0;
-
-        childBox->GetPrefSize(state, prefSize);
-        childBox->GetMinSize(state, minSize);
-        childBox->GetMaxSize(state, maxSize);
+        nsSize prefSize = childBox->GetPrefSize(state);
+        nsSize minSize = childBox->GetMinSize(state);
+        nsSize maxSize = childBox->GetMaxSize(state);
         nsBox::BoundsCheck(minSize, prefSize, maxSize);
 
         mOuter->AddMargin(childBox, minSize);
         mOuter->AddMargin(childBox, prefSize);
         mOuter->AddMargin(childBox, maxSize);
 
+        nscoord flex = 0;
         childBox->GetFlex(state, flex);
 
         nsMargin margin(0,0,0,0);
diff --git a/mozilla/layout/xul/base/src/nsSprocketLayout.cpp b/mozilla/layout/xul/base/src/nsSprocketLayout.cpp
index 67bd48802a4..9912ed8de0d 100644
--- a/mozilla/layout/xul/base/src/nsSprocketLayout.cpp
+++ b/mozilla/layout/xul/base/src/nsSprocketLayout.cpp
@@ -363,19 +363,15 @@ nsSprocketLayout::Layout(nsIBox* aBox, nsBoxLayoutState& aState)
       nscoord width = clientRect.width;
       nscoord height = clientRect.height;
 
-      nsSize prefSize(0,0);
-      nsSize minSize(0,0);
-      nsSize maxSize(0,0);
-      
       if (!childBoxSize->bogus) {
         // We have a valid box size entry.  This entry already contains information about our
         // sizes along the axis of the box (e.g., widths in a horizontal box).  If our default
         // ALIGN is not stretch, however, then we also need to know the child's size along the
         // opposite axis.
         if (!(frameState & NS_STATE_AUTO_STRETCH)) {
-           child->GetPrefSize(aState, prefSize);
-           child->GetMinSize(aState, minSize);
-           child->GetMaxSize(aState, maxSize);
+           nsSize prefSize = child->GetPrefSize(aState);
+           nsSize minSize = child->GetMinSize(aState);
+           nsSize maxSize = child->GetMaxSize(aState);
            nsBox::BoundsCheck(minSize, prefSize, maxSize);
        
            AddMargin(child, prefSize);
@@ -510,8 +506,8 @@ nsSprocketLayout::Layout(nsIBox* aBox, nsBoxLayoutState& aState)
       if (sizeChanged) {
         // Our size is different.  Sanity check against our maximum allowed size to ensure
         // we didn't exceed it.
-        child->GetMinSize(aState, minSize);
-        child->GetMaxSize(aState, maxSize);
+        nsSize minSize = child->GetMinSize(aState);
+        nsSize maxSize = child->GetMaxSize(aState);
         nsBox::BoundsCheckMinMax(minSize, maxSize);
 
         // make sure the size is in our max size.
@@ -818,9 +814,9 @@ nsSprocketLayout::PopulateBoxSizes(nsIBox* aBox, nsBoxLayoutState& aState, nsBox
     // 0 then and not even have to ask for it.
     //if (flexes != 1)  {
 
-      child->GetPrefSize(aState, pref);
-      child->GetMinSize(aState, min);
-      child->GetMaxSize(aState, max);
+      pref = child->GetPrefSize(aState);
+      min = child->GetMinSize(aState);
+      max = child->GetMaxSize(aState);
       child->GetAscent(aState, ascent);
       nsMargin margin;
       child->GetMargin(margin);
@@ -1074,10 +1070,8 @@ nsSprocketLayout::ChildResized(nsIBox* aBox,
             // ok if the height changed then we need to reflow everyone but us at the new height
             // so we will set the changed index to be us. And signal that we need a new pass.
 
-            nsSize max(0,0);
-            nsSize min(0,0);
-            aChild->GetMaxSize(aState, max);
-            aChild->GetMinSize(aState, min);
+            nsSize max = aChild->GetMaxSize(aState);
+            nsSize min = aChild->GetMinSize(aState);
             nsBox::BoundsCheckMinMax(min, max);
             AddMargin(aChild, max);
 
@@ -1112,10 +1106,8 @@ nsSprocketLayout::ChildResized(nsIBox* aBox,
       } 
       
       if (childActualWidth > childLayoutWidth) {
-            nsSize max(0,0);
-            nsSize min(0,0);
-            aChild->GetMinSize(aState, min);
-            aChild->GetMaxSize(aState, max);
+            nsSize min = aChild->GetMinSize(aState);
+            nsSize max = aChild->GetMaxSize(aState);
             nsBox::BoundsCheckMinMax(min, max);
             AddMargin(aChild, max);
 
@@ -1364,8 +1356,7 @@ nsSprocketLayout::GetPrefSize(nsIBox* aBox, nsBoxLayoutState& aState, nsSize& aS
 
       if (!isCollapsed)
       {
-        nsSize pref(0,0);
-        child->GetPrefSize(aState, pref);
+        nsSize pref = child->GetPrefSize(aState);
         AddMargin(child, pref);
 
         if (isEqual) {
@@ -1428,17 +1419,16 @@ nsSprocketLayout::GetMinSize(nsIBox* aBox, nsBoxLayoutState& aState, nsSize& aSi
 
       if (!isCollapsed)
       {
-        nsSize min(0,0);
+        nsSize min = child->GetMinSize(aState);
         nsSize pref(0,0);
         nscoord flex = 0;
 
-        child->GetMinSize(aState, min);        
         child->GetFlex(aState, flex);
         
         // if the child is not flexible then
         // its min size is its pref size.
         if (flex == 0)  {
-            child->GetPrefSize(aState, pref);
+            pref = child->GetPrefSize(aState);
             if (isHorizontal)
                min.width = pref.width;
             else
@@ -1510,10 +1500,8 @@ nsSprocketLayout::GetMaxSize(nsIBox* aBox, nsBoxLayoutState& aState, nsSize& aSi
       if (!isCollapsed)
       {
         // if completely redefined don't even ask our child for its size.
-        nsSize max(NS_INTRINSICSIZE, NS_INTRINSICSIZE);
-        nsSize min(NS_INTRINSICSIZE, NS_INTRINSICSIZE);
-        child->GetMaxSize(aState, max);
-        child->GetMinSize(aState, min);
+        nsSize max = child->GetMaxSize(aState);
+        nsSize min = child->GetMinSize(aState);
         nsBox::BoundsCheckMinMax(min, max);
 
         AddMargin(child, max);
diff --git a/mozilla/layout/xul/base/src/nsStackLayout.cpp b/mozilla/layout/xul/base/src/nsStackLayout.cpp
index 3bb7dc20fdf..6b4fa126d00 100644
--- a/mozilla/layout/xul/base/src/nsStackLayout.cpp
+++ b/mozilla/layout/xul/base/src/nsStackLayout.cpp
@@ -88,8 +88,7 @@ nsStackLayout::GetPrefSize(nsIBox* aBox, nsBoxLayoutState& aState, nsSize& aSize
   aBox->GetChildBox(&child);
  
   while (child) {  
-    nsSize pref(0,0);
-    child->GetPrefSize(aState, pref);
+    nsSize pref = child->GetPrefSize(aState);
 
     AddMargin(child, pref);
     AddOffset(aState, child, pref);
@@ -117,8 +116,7 @@ nsStackLayout::GetMinSize(nsIBox* aBox, nsBoxLayoutState& aState, nsSize& aSize)
   aBox->GetChildBox(&child);
    
   while (child) {  
-    nsSize min(0,0);
-    child->GetMinSize(aState, min);        
+    nsSize min = child->GetMinSize(aState);
     AddMargin(child, min);
     AddOffset(aState, child, min);
     AddLargestSize(aSize, min);
@@ -145,10 +143,8 @@ nsStackLayout::GetMaxSize(nsIBox* aBox, nsBoxLayoutState& aState, nsSize& aSize)
   aBox->GetChildBox(&child);
    
   while (child) {  
-    nsSize max(NS_INTRINSICSIZE, NS_INTRINSICSIZE);
-    child->GetMaxSize(aState, max);
-    nsSize min(NS_INTRINSICSIZE, NS_INTRINSICSIZE);
-    child->GetMinSize(aState, min);
+    nsSize max = child->GetMaxSize(aState);
+    nsSize min = child->GetMinSize(aState);
     nsBox::BoundsCheckMinMax(min, max);
 
     AddMargin(child, max);
@@ -298,8 +294,7 @@ nsStackLayout::Layout(nsIBox* aBox, nsBoxLayoutState& aState)
           // If we have an offset, we don't stretch the child.  Just use
           // its preferred size.
           if (offsetSpecified) {
-            nsSize pref(0,0);
-            child->GetPrefSize(aState, pref);
+            nsSize pref = child->GetPrefSize(aState);
             childRect.width = pref.width;
             childRect.height = pref.height;
           }
diff --git a/mozilla/layout/xul/base/src/nsTextBoxFrame.cpp b/mozilla/layout/xul/base/src/nsTextBoxFrame.cpp
index 9167a79d073..27d3ce5477e 100644
--- a/mozilla/layout/xul/base/src/nsTextBoxFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsTextBoxFrame.cpp
@@ -854,42 +854,41 @@ nsTextBoxFrame::CalcTextSize(nsBoxLayoutState& aBoxLayoutState)
 /**
  * Ok return our dimensions
  */
-NS_IMETHODIMP
-nsTextBoxFrame::GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)
+nsSize
+nsTextBoxFrame::GetPrefSize(nsBoxLayoutState& aBoxLayoutState)
 {
-    DISPLAY_PREF_SIZE(this, aSize);
     CalcTextSize(aBoxLayoutState);
 
-    aSize = mTextSize;
+    nsSize size = mTextSize;
+    DISPLAY_PREF_SIZE(this, size);
 
-    AddBorderAndPadding(aSize);
-    AddInset(aSize);
-    nsIBox::AddCSSPrefSize(aBoxLayoutState, this, aSize);
+    AddBorderAndPadding(size);
+    AddInset(size);
+    nsIBox::AddCSSPrefSize(aBoxLayoutState, this, size);
 
-    return NS_OK;
+    return size;
 }
 
 /**
  * Ok return our dimensions
  */
-NS_IMETHODIMP
-nsTextBoxFrame::GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)
+nsSize
+nsTextBoxFrame::GetMinSize(nsBoxLayoutState& aBoxLayoutState)
 {
-    DISPLAY_MIN_SIZE(this, aSize);
     CalcTextSize(aBoxLayoutState);
 
-    aSize = mTextSize;
+    nsSize size = mTextSize;
+    DISPLAY_MIN_SIZE(this, size);
 
-     // if there is cropping our min width becomes our border and  padding
-    if (mCropType != CropNone) {
-       aSize.width = 0;
-    }
+    // if there is cropping our min width becomes our border and padding
+    if (mCropType != CropNone)
+        size.width = 0;
 
-    AddBorderAndPadding(aSize);
-    AddInset(aSize);
-    nsIBox::AddCSSMinSize(aBoxLayoutState, this, aSize);
+    AddBorderAndPadding(size);
+    AddInset(size);
+    nsIBox::AddCSSMinSize(aBoxLayoutState, this, size);
 
-    return NS_OK;
+    return size;
 }
 
 NS_IMETHODIMP
diff --git a/mozilla/layout/xul/base/src/nsTextBoxFrame.h b/mozilla/layout/xul/base/src/nsTextBoxFrame.h
index 568625a0b22..6a323ae0fb8 100644
--- a/mozilla/layout/xul/base/src/nsTextBoxFrame.h
+++ b/mozilla/layout/xul/base/src/nsTextBoxFrame.h
@@ -48,8 +48,8 @@ class nsTextBoxFrame : public nsTextBoxFrameSuper
 public:
 
   // nsIBox
-  NS_IMETHOD GetPrefSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
+  virtual nsSize GetPrefSize(nsBoxLayoutState& aBoxLayoutState);
+  virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState);
   NS_IMETHOD GetAscent(nsBoxLayoutState& aBoxLayoutState, nscoord& aAscent);
   NS_IMETHOD DoLayout(nsBoxLayoutState& aBoxLayoutState);
   virtual void MarkIntrinsicWidthsDirty();
diff --git a/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp b/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp
index f7e840f5f28..eac9e20eb8b 100644
--- a/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp
+++ b/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp
@@ -217,20 +217,21 @@ nsTreeBodyFrame::Init(nsIContent*     aContent,
   return rv;
 }
 
-NS_IMETHODIMP
-nsTreeBodyFrame::GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)
+nsSize
+nsTreeBodyFrame::GetMinSize(nsBoxLayoutState& aBoxLayoutState)
 {
   EnsureView();
 
   nsIContent* baseElement = GetBaseElement();
 
+  nsSize min(0,0);
   PRInt32 desiredRows;
   if (NS_UNLIKELY(!baseElement)) {
     desiredRows = 0;
   }
   else if (baseElement->Tag() == nsGkAtoms::select &&
            baseElement->IsNodeOfType(nsINode::eHTML)) {
-    aSize.width = CalcMaxRowWidth();
+    min.width = CalcMaxRowWidth();
     nsAutoString size;
     baseElement->GetAttr(kNameSpaceID_None, nsGkAtoms::size, size);
     if (!size.IsEmpty()) {
@@ -245,7 +246,6 @@ nsTreeBodyFrame::GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)
   }
   else {
     // tree
-    aSize.width = 0;
     nsAutoString rows;
     baseElement->GetAttr(kNameSpaceID_None, nsGkAtoms::rows, rows);
     if (!rows.IsEmpty()) {
@@ -258,13 +258,13 @@ nsTreeBodyFrame::GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize)
     }
   }
 
-  aSize.height = mRowHeight * desiredRows;
+  min.height = mRowHeight * desiredRows;
 
-  AddBorderAndPadding(aSize);
-  AddInset(aSize);
-  nsIBox::AddCSSMinSize(aBoxLayoutState, this, aSize);
+  AddBorderAndPadding(min);
+  AddInset(min);
+  nsIBox::AddCSSMinSize(aBoxLayoutState, this, min);
 
-  return NS_OK;
+  return min;
 }
 
 nscoord
diff --git a/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.h b/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.h
index 002631cd6f9..849fd7e9a92 100644
--- a/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.h
+++ b/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.h
@@ -86,7 +86,7 @@ public:
   NS_DECL_NSITREEBOXOBJECT
 
   // nsIBox
-  NS_IMETHOD GetMinSize(nsBoxLayoutState& aBoxLayoutState, nsSize& aSize);
+  virtual nsSize GetMinSize(nsBoxLayoutState& aBoxLayoutState);
   NS_IMETHOD SetBounds(nsBoxLayoutState& aBoxLayoutState, const nsRect& aRect,
                        PRBool aRemoveOverflowArea = PR_FALSE);