diff --git a/mozilla/layout/generic/nsAbsoluteContainingBlock.cpp b/mozilla/layout/generic/nsAbsoluteContainingBlock.cpp
index fcff042a6c8..21ba08eb7af 100644
--- a/mozilla/layout/generic/nsAbsoluteContainingBlock.cpp
+++ b/mozilla/layout/generic/nsAbsoluteContainingBlock.cpp
@@ -143,6 +143,7 @@ nsAbsoluteContainingBlock::Reflow(nsContainerFrame*        aDelegatingFrame,
                                   nsReflowStatus&          aReflowStatus,
                                   nscoord                  aContainingBlockWidth,
                                   nscoord                  aContainingBlockHeight,
+                                  PRBool                   aConstrainHeight,
                                   PRBool                   aCBWidthChanged,
                                   PRBool                   aCBHeightChanged,
                                   nsRect*                  aChildBounds)
@@ -164,7 +165,7 @@ nsAbsoluteContainingBlock::Reflow(nsContainerFrame*        aDelegatingFrame,
       nsReflowStatus  kidStatus = NS_FRAME_COMPLETE;
       ReflowAbsoluteFrame(aDelegatingFrame, aPresContext, aReflowState,
                           aContainingBlockWidth, aContainingBlockHeight,
-                          kidFrame, kidStatus, aChildBounds);
+                          aConstrainHeight, kidFrame, kidStatus, aChildBounds);
       nsIFrame* nextFrame = kidFrame->GetNextInFlow();
       if (!NS_FRAME_IS_FULLY_COMPLETE(kidStatus)) {
         // Need a continuation
@@ -358,6 +359,7 @@ nsAbsoluteContainingBlock::ReflowAbsoluteFrame(nsIFrame*                aDelegat
                                                const nsHTMLReflowState& aReflowState,
                                                nscoord                  aContainingBlockWidth,
                                                nscoord                  aContainingBlockHeight,
+                                               PRBool                   aConstrainHeight,
                                                nsIFrame*                aKidFrame,
                                                nsReflowStatus&          aStatus,
                                                nsRect*                  aChildBounds)
@@ -415,8 +417,8 @@ nsAbsoluteContainingBlock::ReflowAbsoluteFrame(nsIFrame*                aDelegat
   aKidFrame->WillReflow(aPresContext);
 
   PRBool constrainHeight = (aReflowState.availableHeight != NS_UNCONSTRAINEDSIZE)
-    && (nsGkAtoms::fixedList != GetChildListName())
-       // Don't split fixed frames
+    && aConstrainHeight
+       // Don't split if told not to (e.g. for fixed frames)
     && (aDelegatingFrame->GetType() != nsGkAtoms::positionedInlineFrame)
        //XXX we don't handle splitting frames for inline absolute containing blocks yet
     && (aKidFrame->GetRect().y <= aReflowState.availableHeight);
diff --git a/mozilla/layout/generic/nsAbsoluteContainingBlock.h b/mozilla/layout/generic/nsAbsoluteContainingBlock.h
index 38d48798ac0..80202cc259d 100644
--- a/mozilla/layout/generic/nsAbsoluteContainingBlock.h
+++ b/mozilla/layout/generic/nsAbsoluteContainingBlock.h
@@ -71,14 +71,18 @@ class nsAbsoluteContainingBlock
 {
 public:
   nsAbsoluteContainingBlock(nsIAtom* aChildListName)
+#ifdef DEBUG
     : mChildListName(aChildListName)
+#endif
   {
     NS_ASSERTION(mChildListName == nsGkAtoms::absoluteList ||
                  mChildListName == nsGkAtoms::fixedList,
                  "should either represent position:fixed or absolute content");
   }
 
+#ifdef DEBUG
   nsIAtom* GetChildListName() const { return mChildListName; }
+#endif
 
   nsresult FirstChild(const nsIFrame* aDelegatingFrame,
                       nsIAtom*        aListName,
@@ -116,6 +120,7 @@ public:
                   nsReflowStatus&          aReflowStatus,
                   nscoord                  aContainingBlockWidth,
                   nscoord                  aContainingBlockHeight,
+                  PRBool                   aConstrainHeight,
                   PRBool                   aCBWidthChanged,
                   PRBool                   aCBHeightChanged,
                   nsRect*                  aChildBounds = nsnull);
@@ -137,6 +142,7 @@ protected:
                                const nsHTMLReflowState& aReflowState,
                                nscoord                  aContainingBlockWidth,
                                nscoord                  aContainingBlockHeight,
+                               PRBool                   aConstrainHeight,
                                nsIFrame*                aKidFrame,
                                nsReflowStatus&          aStatus,
                                nsRect*                  aChildBounds);
@@ -144,11 +150,13 @@ protected:
 protected:
   nsFrameList mAbsoluteFrames;  // additional named child list
 
+#ifdef DEBUG
   nsIAtom* const mChildListName; // nsGkAtoms::fixedList or nsGkAtoms::absoluteList
 
   // helper routine for debug printout
   void PrettyUC(nscoord aSize,
                 char*   aBuf);
+#endif
 };
 
 #endif /* nsnsAbsoluteContainingBlock_h___ */
diff --git a/mozilla/layout/generic/nsBlockFrame.cpp b/mozilla/layout/generic/nsBlockFrame.cpp
index 22b6158b603..76d2a786553 100644
--- a/mozilla/layout/generic/nsBlockFrame.cpp
+++ b/mozilla/layout/generic/nsBlockFrame.cpp
@@ -1136,7 +1136,7 @@ nsBlockFrame::Reflow(nsPresContext*           aPresContext,
     rv = mAbsoluteContainer.Reflow(this, aPresContext, aReflowState,
                                    state.mReflowStatus,
                                    containingBlockSize.width,
-                                   containingBlockSize.height,
+                                   containingBlockSize.height, PR_TRUE,
                                    cbWidthChanged, cbHeightChanged,
                                    &childBounds);
 
diff --git a/mozilla/layout/generic/nsInlineFrame.cpp b/mozilla/layout/generic/nsInlineFrame.cpp
index 495cd403c7e..5deb9778012 100644
--- a/mozilla/layout/generic/nsInlineFrame.cpp
+++ b/mozilla/layout/generic/nsInlineFrame.cpp
@@ -1133,7 +1133,7 @@ nsPositionedInlineFrame::Reflow(nsPresContext*          aPresContext,
     // That will all be done by nsLineLayout::RelativePositionFrames.
     rv = mAbsoluteContainer.Reflow(this, aPresContext, aReflowState, aStatus,
                                    containingBlockWidth, containingBlockHeight,
-                                   PR_TRUE, PR_TRUE, // XXX could be optimized
+                                   PR_TRUE, PR_TRUE, PR_TRUE, // XXX could be optimized
                                    &aDesiredSize.mOverflowArea);
   }
 
diff --git a/mozilla/layout/generic/nsPageContentFrame.cpp b/mozilla/layout/generic/nsPageContentFrame.cpp
index 0eae99025bb..b5eb6be0c8b 100644
--- a/mozilla/layout/generic/nsPageContentFrame.cpp
+++ b/mozilla/layout/generic/nsPageContentFrame.cpp
@@ -149,7 +149,7 @@ nsPageContentFrame::Reflow(nsPresContext*           aPresContext,
   mFixedContainer.Reflow(this, aPresContext, aReflowState, aStatus,
                          aReflowState.availableWidth,
                          aReflowState.availableHeight,
-                         PR_TRUE, PR_TRUE); // XXX could be optimized
+                         PR_FALSE, PR_TRUE, PR_TRUE); // XXX could be optimized
 
   // Return our desired size
   aDesiredSize.width = aReflowState.availableWidth;
diff --git a/mozilla/layout/generic/nsViewportFrame.cpp b/mozilla/layout/generic/nsViewportFrame.cpp
index d602397cbcb..43f3c4bbd8d 100644
--- a/mozilla/layout/generic/nsViewportFrame.cpp
+++ b/mozilla/layout/generic/nsViewportFrame.cpp
@@ -319,7 +319,7 @@ ViewportFrame::Reflow(nsPresContext*          aPresContext,
   rv = mFixedContainer.Reflow(this, aPresContext, reflowState, aStatus,
                               reflowState.ComputedWidth(),
                               reflowState.ComputedHeight(),
-                              PR_TRUE, PR_TRUE); // XXX could be optimized
+                              PR_FALSE, PR_TRUE, PR_TRUE); // XXX could be optimized
 
   // If we were dirty then do a repaint
   if (GetStateBits() & NS_FRAME_IS_DIRTY) {