diff --git a/mozilla/layout/base/public/nsHTMLReflowMetrics.h b/mozilla/layout/base/public/nsHTMLReflowMetrics.h
index 026b59242a0..4f50ae414f7 100644
--- a/mozilla/layout/base/public/nsHTMLReflowMetrics.h
+++ b/mozilla/layout/base/public/nsHTMLReflowMetrics.h
@@ -96,6 +96,14 @@ struct nsCollapsingMargin {
           mMostNeg = aCoord;
       }
 
+    void Include(const nsCollapsingMargin& aOther)
+      {
+        if (aOther.mMostPos > mMostPos)
+          mMostPos = aOther.mMostPos;
+        if (aOther.mMostNeg < mMostNeg)
+          mMostNeg = aOther.mMostNeg;
+      }
+
     void Zero()
       {
         mMostPos = 0;
diff --git a/mozilla/layout/generic/nsBlockFrame.cpp b/mozilla/layout/generic/nsBlockFrame.cpp
index 624ef25ee48..8e176380944 100644
--- a/mozilla/layout/generic/nsBlockFrame.cpp
+++ b/mozilla/layout/generic/nsBlockFrame.cpp
@@ -757,8 +757,8 @@ nsBlockFrame::Reflow(nsIPresContext*          aPresContext,
                                          containingBlockHeight,
                                          handled);
 
-    // If the incremental reflow command was handled by the absolute positioning
-    // code, then we're all done
+    // If the incremental reflow command was handled by the absolute
+    // positioning code, then we're all done.
     if (handled) {
       // Just return our current size as our desired size.
       aMetrics.width = mRect.width;
@@ -1370,14 +1370,8 @@ nsBlockFrame::ComputeFinalSize(const nsHTMLReflowState& aReflowState,
     // because we can't shrink any smaller.
     maxHeight = aMetrics.height;
 
-    // Don't carry out a bottom margin when our height is fixed
-    // unless the bottom of the last line adjoins the bottom of our
-    // content area.
-    if (!aState.GetFlag(BRS_ISBOTTOMMARGINROOT)) {
-      if (aState.mY + aState.mPrevBottomMargin.get() != aMetrics.height) {
-        aState.mPrevBottomMargin.Zero();
-      }
-    }
+    // Don't carry out a bottom margin when our height is fixed.
+    aState.mPrevBottomMargin.Zero();
   }
   else {
     nscoord autoHeight = aState.mY;
@@ -3344,8 +3338,9 @@ nsBlockFrame::ReflowBlockFrame(nsBlockReflowState& aState,
     PRBool isAdjacentWithTop = aState.IsAdjacentWithTop();
     nsCollapsingMargin collapsedBottomMargin;
     nsRect combinedArea(0,0,0,0);
-    *aKeepReflowGoing = brc.PlaceBlock(blockHtmlRS, isAdjacentWithTop, computedOffsets,
-                                       collapsedBottomMargin, aLine->mBounds, combinedArea);
+    *aKeepReflowGoing = brc.PlaceBlock(blockHtmlRS, isAdjacentWithTop,
+                                       computedOffsets, collapsedBottomMargin,
+                                       aLine->mBounds, combinedArea);
     aLine->SetCarriedOutBottomMargin(collapsedBottomMargin);
 
     if (aState.GetFlag(BRS_SHRINKWRAPWIDTH)) {
diff --git a/mozilla/layout/generic/nsBlockReflowContext.cpp b/mozilla/layout/generic/nsBlockReflowContext.cpp
index ab967910483..201abfac560 100644
--- a/mozilla/layout/generic/nsBlockReflowContext.cpp
+++ b/mozilla/layout/generic/nsBlockReflowContext.cpp
@@ -409,7 +409,7 @@ nsBlockReflowContext::ReflowBlock(const nsRect&       aSpace,
       aFrameRS.availableHeight -= aPrevBottomMargin.get();
     }
   }
-  mTopMargin = aPrevBottomMargin.get();
+  mTopMargin = aPrevBottomMargin;
 
   // Compute x/y coordinate where reflow will begin. Use the rules
   // from 10.3.3 to determine what to apply. At this point in the
@@ -419,7 +419,7 @@ nsBlockReflowContext::ReflowBlock(const nsRect&       aSpace,
   mStyleMargin = aFrameRS.mStyleMargin;
   mStylePadding = aFrameRS.mStylePadding;
   nscoord x;
-  nscoord y = mSpace.y + mTopMargin;
+  nscoord y = mSpace.y + mTopMargin.get();
 
   // If it's a right floated element, then calculate the x-offset
   // differently
@@ -687,13 +687,12 @@ nsBlockReflowContext::PlaceBlock(const nsHTMLReflowState& aReflowState,
 
     y = mSpace.y;
 
-    // Empty blocks do not have anything special done to them and they
-    // always fit. Note: don't force the width to 0
-    nsRect r(x, y, mMetrics.width, 0);
-
     // Now place the frame and complete the reflow process
     nsContainerFrame::FinishReflowChild(mFrame, mPresContext, &aReflowState, mMetrics, x, y, 0);
-    aInFlowBounds = r;
+
+    // Empty blocks do not have anything special done to them and they
+    // always fit. Note: don't force the width to 0
+    aInFlowBounds = nsRect(x, y, mMetrics.width, 0);
 
     // Retain combined area information in case we contain a floater
     // and nothing else.
@@ -773,7 +772,7 @@ nsBlockReflowContext::PlaceBlock(const nsHTMLReflowState& aReflowState,
         // auto top/bottom margins are always zero)
 
         // XXXldb Should it?
-        m->height += mTopMargin + mBottomMargin;
+        m->height += mTopMargin.get() + mBottomMargin;
 #endif
       }
     }
diff --git a/mozilla/layout/generic/nsBlockReflowContext.h b/mozilla/layout/generic/nsBlockReflowContext.h
index 838f6305463..d31128a651a 100644
--- a/mozilla/layout/generic/nsBlockReflowContext.h
+++ b/mozilla/layout/generic/nsBlockReflowContext.h
@@ -82,7 +82,7 @@ public:
   }
 
   nscoord GetTopMargin() const {
-    return mTopMargin;
+    return mTopMargin.get();
   }
 
   const nsMargin& GetMargin() const {
@@ -128,7 +128,7 @@ protected:
   nsMargin mMargin;
   nscoord mX, mY;
   nsHTMLReflowMetrics mMetrics;
-  nscoord mTopMargin;
+  nsCollapsingMargin mTopMargin;
   nsSize mMaxElementSize;
   PRPackedBool mIsTable;
   PRPackedBool mComputeMaximumWidth;
diff --git a/mozilla/layout/generic/nsBlockReflowState.cpp b/mozilla/layout/generic/nsBlockReflowState.cpp
index 1c4ae0200a6..84dcf843c4b 100644
--- a/mozilla/layout/generic/nsBlockReflowState.cpp
+++ b/mozilla/layout/generic/nsBlockReflowState.cpp
@@ -448,11 +448,10 @@ nsBlockReflowState::ReconstructMarginAbove(nsLineList::iterator aLine)
   mPrevBottomMargin.Zero();
   nsBlockFrame *block = mBlock;
 
-  const nsStyleText* styleText = NS_STATIC_CAST(const nsStyleText*,
-      block->mStyleContext->GetStyleData(eStyleStruct_Text));
-  PRBool isPre =
-      ((NS_STYLE_WHITESPACE_PRE == styleText->mWhiteSpace) ||
-       (NS_STYLE_WHITESPACE_MOZ_PRE_WRAP == styleText->mWhiteSpace));
+  const nsStyleText* styleText;
+  ::GetStyleData(block, &styleText);
+  PRBool isPre = NS_STYLE_WHITESPACE_PRE == styleText->mWhiteSpace ||
+                 NS_STYLE_WHITESPACE_MOZ_PRE_WRAP == styleText->mWhiteSpace;
 
   nsCompatibility mode;
   mPresContext->GetCompatibilityMode(&mode);
diff --git a/mozilla/layout/generic/nsHTMLReflowMetrics.h b/mozilla/layout/generic/nsHTMLReflowMetrics.h
index 026b59242a0..4f50ae414f7 100644
--- a/mozilla/layout/generic/nsHTMLReflowMetrics.h
+++ b/mozilla/layout/generic/nsHTMLReflowMetrics.h
@@ -96,6 +96,14 @@ struct nsCollapsingMargin {
           mMostNeg = aCoord;
       }
 
+    void Include(const nsCollapsingMargin& aOther)
+      {
+        if (aOther.mMostPos > mMostPos)
+          mMostPos = aOther.mMostPos;
+        if (aOther.mMostNeg < mMostNeg)
+          mMostNeg = aOther.mMostNeg;
+      }
+
     void Zero()
       {
         mMostPos = 0;
diff --git a/mozilla/layout/html/base/src/nsBlockFrame.cpp b/mozilla/layout/html/base/src/nsBlockFrame.cpp
index 624ef25ee48..8e176380944 100644
--- a/mozilla/layout/html/base/src/nsBlockFrame.cpp
+++ b/mozilla/layout/html/base/src/nsBlockFrame.cpp
@@ -757,8 +757,8 @@ nsBlockFrame::Reflow(nsIPresContext*          aPresContext,
                                          containingBlockHeight,
                                          handled);
 
-    // If the incremental reflow command was handled by the absolute positioning
-    // code, then we're all done
+    // If the incremental reflow command was handled by the absolute
+    // positioning code, then we're all done.
     if (handled) {
       // Just return our current size as our desired size.
       aMetrics.width = mRect.width;
@@ -1370,14 +1370,8 @@ nsBlockFrame::ComputeFinalSize(const nsHTMLReflowState& aReflowState,
     // because we can't shrink any smaller.
     maxHeight = aMetrics.height;
 
-    // Don't carry out a bottom margin when our height is fixed
-    // unless the bottom of the last line adjoins the bottom of our
-    // content area.
-    if (!aState.GetFlag(BRS_ISBOTTOMMARGINROOT)) {
-      if (aState.mY + aState.mPrevBottomMargin.get() != aMetrics.height) {
-        aState.mPrevBottomMargin.Zero();
-      }
-    }
+    // Don't carry out a bottom margin when our height is fixed.
+    aState.mPrevBottomMargin.Zero();
   }
   else {
     nscoord autoHeight = aState.mY;
@@ -3344,8 +3338,9 @@ nsBlockFrame::ReflowBlockFrame(nsBlockReflowState& aState,
     PRBool isAdjacentWithTop = aState.IsAdjacentWithTop();
     nsCollapsingMargin collapsedBottomMargin;
     nsRect combinedArea(0,0,0,0);
-    *aKeepReflowGoing = brc.PlaceBlock(blockHtmlRS, isAdjacentWithTop, computedOffsets,
-                                       collapsedBottomMargin, aLine->mBounds, combinedArea);
+    *aKeepReflowGoing = brc.PlaceBlock(blockHtmlRS, isAdjacentWithTop,
+                                       computedOffsets, collapsedBottomMargin,
+                                       aLine->mBounds, combinedArea);
     aLine->SetCarriedOutBottomMargin(collapsedBottomMargin);
 
     if (aState.GetFlag(BRS_SHRINKWRAPWIDTH)) {
diff --git a/mozilla/layout/html/base/src/nsBlockReflowContext.cpp b/mozilla/layout/html/base/src/nsBlockReflowContext.cpp
index ab967910483..201abfac560 100644
--- a/mozilla/layout/html/base/src/nsBlockReflowContext.cpp
+++ b/mozilla/layout/html/base/src/nsBlockReflowContext.cpp
@@ -409,7 +409,7 @@ nsBlockReflowContext::ReflowBlock(const nsRect&       aSpace,
       aFrameRS.availableHeight -= aPrevBottomMargin.get();
     }
   }
-  mTopMargin = aPrevBottomMargin.get();
+  mTopMargin = aPrevBottomMargin;
 
   // Compute x/y coordinate where reflow will begin. Use the rules
   // from 10.3.3 to determine what to apply. At this point in the
@@ -419,7 +419,7 @@ nsBlockReflowContext::ReflowBlock(const nsRect&       aSpace,
   mStyleMargin = aFrameRS.mStyleMargin;
   mStylePadding = aFrameRS.mStylePadding;
   nscoord x;
-  nscoord y = mSpace.y + mTopMargin;
+  nscoord y = mSpace.y + mTopMargin.get();
 
   // If it's a right floated element, then calculate the x-offset
   // differently
@@ -687,13 +687,12 @@ nsBlockReflowContext::PlaceBlock(const nsHTMLReflowState& aReflowState,
 
     y = mSpace.y;
 
-    // Empty blocks do not have anything special done to them and they
-    // always fit. Note: don't force the width to 0
-    nsRect r(x, y, mMetrics.width, 0);
-
     // Now place the frame and complete the reflow process
     nsContainerFrame::FinishReflowChild(mFrame, mPresContext, &aReflowState, mMetrics, x, y, 0);
-    aInFlowBounds = r;
+
+    // Empty blocks do not have anything special done to them and they
+    // always fit. Note: don't force the width to 0
+    aInFlowBounds = nsRect(x, y, mMetrics.width, 0);
 
     // Retain combined area information in case we contain a floater
     // and nothing else.
@@ -773,7 +772,7 @@ nsBlockReflowContext::PlaceBlock(const nsHTMLReflowState& aReflowState,
         // auto top/bottom margins are always zero)
 
         // XXXldb Should it?
-        m->height += mTopMargin + mBottomMargin;
+        m->height += mTopMargin.get() + mBottomMargin;
 #endif
       }
     }
diff --git a/mozilla/layout/html/base/src/nsBlockReflowContext.h b/mozilla/layout/html/base/src/nsBlockReflowContext.h
index 838f6305463..d31128a651a 100644
--- a/mozilla/layout/html/base/src/nsBlockReflowContext.h
+++ b/mozilla/layout/html/base/src/nsBlockReflowContext.h
@@ -82,7 +82,7 @@ public:
   }
 
   nscoord GetTopMargin() const {
-    return mTopMargin;
+    return mTopMargin.get();
   }
 
   const nsMargin& GetMargin() const {
@@ -128,7 +128,7 @@ protected:
   nsMargin mMargin;
   nscoord mX, mY;
   nsHTMLReflowMetrics mMetrics;
-  nscoord mTopMargin;
+  nsCollapsingMargin mTopMargin;
   nsSize mMaxElementSize;
   PRPackedBool mIsTable;
   PRPackedBool mComputeMaximumWidth;
diff --git a/mozilla/layout/html/base/src/nsBlockReflowState.cpp b/mozilla/layout/html/base/src/nsBlockReflowState.cpp
index 1c4ae0200a6..84dcf843c4b 100644
--- a/mozilla/layout/html/base/src/nsBlockReflowState.cpp
+++ b/mozilla/layout/html/base/src/nsBlockReflowState.cpp
@@ -448,11 +448,10 @@ nsBlockReflowState::ReconstructMarginAbove(nsLineList::iterator aLine)
   mPrevBottomMargin.Zero();
   nsBlockFrame *block = mBlock;
 
-  const nsStyleText* styleText = NS_STATIC_CAST(const nsStyleText*,
-      block->mStyleContext->GetStyleData(eStyleStruct_Text));
-  PRBool isPre =
-      ((NS_STYLE_WHITESPACE_PRE == styleText->mWhiteSpace) ||
-       (NS_STYLE_WHITESPACE_MOZ_PRE_WRAP == styleText->mWhiteSpace));
+  const nsStyleText* styleText;
+  ::GetStyleData(block, &styleText);
+  PRBool isPre = NS_STYLE_WHITESPACE_PRE == styleText->mWhiteSpace ||
+                 NS_STYLE_WHITESPACE_MOZ_PRE_WRAP == styleText->mWhiteSpace;
 
   nsCompatibility mode;
   mPresContext->GetCompatibilityMode(&mode);