Horizontal under/overflow events are not dispatched. b=363933 r+sr=dbaron

layout/generic/nsGfxScrollFrame.cpp

@@ -21,6 +21,7 @@
  *
  * Contributor(s):
  *   Pierre Phaneuf <pp@ludusdesign.com>
+ *   Mats Palmgren <mats.palmgren@bredband.net>
  *
  * Alternatively, the contents of this file may be used under the terms of
  * either of the GNU General Public License Version 2 or later (the "GPL"),
@@ -2017,8 +2018,8 @@ nsXULScrollFrame::LayoutScrollArea(nsBoxLayoutState& aState, const nsRect& aRect
 
 void nsGfxScrollFrameInner::PostOverflowEvents()
 {
-  nsSize childSize = mScrolledFrame->GetSize();
   nsSize scrollportSize = GetScrollPortSize();
+  nsSize childSize = GetScrolledRect(scrollportSize).Size();
     
   PRBool newVerticalOverflow = childSize.height > scrollportSize.height;
   PRBool vertChanged = mVerticalOverflow != newVerticalOverflow;