Merge 126591 - Crash in RenderTableCell::borderTop() due to custom scrollbars after r124168

Source/WebCore/rendering/RenderScrollbarPart.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 73 matching lines @@
     if (!length.isIntrinsicOrAuto() || (sizeType == MinSize && length.isAuto()))
         return minimumValueForLength(length, containingLength, renderView);
     return ScrollbarTheme::theme()->scrollbarThickness();
 }
 
 void RenderScrollbarPart::computeScrollbarWidth()
 {
     if (!m_scrollbar->owningRenderer())
         return;
     RenderView* renderView = view();
-    int visibleSize = m_scrollbar->owningRenderer()->width() - m_scrollbar->owningRenderer()->borderLeft() - m_scrollbar->owningRenderer()->borderRight();
+    // FIXME: We are querying layout information but nothing guarantees that it's up-to-date, especially since we are called at style change.
+    // FIXME: Querying the style's border information doesn't work on table cells with collapsing borders.
+    int visibleSize = m_scrollbar->owningRenderer()->width() - m_scrollbar->owningRenderer()->style()->borderLeftWidth() - m_scrollbar->owningRenderer()->style()->borderRightWidth();
     int w = calcScrollbarThicknessUsing(MainOrPreferredSize, style()->width(), visibleSize, renderView);
     int minWidth = calcScrollbarThicknessUsing(MinSize, style()->minWidth(), visibleSize, renderView);
     int maxWidth = style()->maxWidth().isUndefined() ? w : calcScrollbarThicknessUsing(MaxSize, style()->maxWidth(), visibleSize, renderView);
     setWidth(max(minWidth, min(maxWidth, w)));
     
     // Buttons and track pieces can all have margins along the axis of the scrollbar. 
     m_marginBox.setLeft(minimumValueForLength(style()->marginLeft(), visibleSize, renderView));
     m_marginBox.setRight(minimumValueForLength(style()->marginRight(), visibleSize, renderView));
 }
 
 void RenderScrollbarPart::computeScrollbarHeight()
 {
     if (!m_scrollbar->owningRenderer())
         return;
     RenderView* renderView = view();
-    int visibleSize = m_scrollbar->owningRenderer()->height() -  m_scrollbar->owningRenderer()->borderTop() - m_scrollbar->owningRenderer()->borderBottom();
+    // FIXME: We are querying layout information but nothing guarantees that it's up-to-date, especially since we are called at style change.
+    // FIXME: Querying the style's border information doesn't work on table cells with collapsing borders.
+    int visibleSize = m_scrollbar->owningRenderer()->height() -  m_scrollbar->owningRenderer()->style()->borderTopWidth() - m_scrollbar->owningRenderer()->style()->borderBottomWidth();
     int h = calcScrollbarThicknessUsing(MainOrPreferredSize, style()->height(), visibleSize, renderView);
     int minHeight = calcScrollbarThicknessUsing(MinSize, style()->minHeight(), visibleSize, renderView);
     int maxHeight = style()->maxHeight().isUndefined() ? h : calcScrollbarThicknessUsing(MaxSize, style()->maxHeight(), visibleSize, renderView);
     setHeight(max(minHeight, min(maxHeight, h)));
 
     // Buttons and track pieces can all have margins along the axis of the scrollbar. 
     m_marginBox.setTop(minimumValueForLength(style()->marginTop(), visibleSize, renderView));
     m_marginBox.setBottom(minimumValueForLength(style()->marginBottom(), visibleSize, renderView));
 }
 
@@ skipping 64 matching lines @@
 }
 
 RenderObject* RenderScrollbarPart::rendererOwningScrollbar() const
 {
     if (!m_scrollbar)
         return 0;
     return m_scrollbar->owningRenderer();
 }
 
 }