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

Source/WebCore/rendering/RenderScrollbarPart.cpp

Index: Source/WebCore/rendering/RenderScrollbarPart.cpp
===================================================================
--- Source/WebCore/rendering/RenderScrollbarPart.cpp	(revision 126824)
+++ Source/WebCore/rendering/RenderScrollbarPart.cpp	(working copy)
@@ -91,7 +91,9 @@
     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);
@@ -107,7 +109,9 @@
     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);