Call scrollbarsChanged in PLSA::updateAfterStyleChange.

third_party/WebKit/Source/core/layout/LayoutBlock.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc.
  *               All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 263 matching lines @@
   }
   void setMarginBeforeForChild(LayoutBox& child, LayoutUnit value) const {
     child.setMarginBefore(value, style());
   }
   void setMarginAfterForChild(LayoutBox& child, LayoutUnit value) const {
     child.setMarginAfter(value, style());
   }
   LayoutUnit collapsedMarginBeforeForChild(const LayoutBox& child) const;
   LayoutUnit collapsedMarginAfterForChild(const LayoutBox& child) const;
 
-  virtual void scrollbarsChanged(bool /*horizontalScrollbarChanged*/,
-                                 bool /*verticalScrollbarChanged*/);
+  enum ScrollbarChangeContext { StyleChange, Layout };
+  virtual void scrollbarsChanged(bool horizontalScrollbarChanged,
+                                 bool verticalScrollbarChanged,
+                                 ScrollbarChangeContext = Layout);
 
   LayoutUnit availableLogicalWidthForContent() const {
     return (logicalRightOffsetForContent() - logicalLeftOffsetForContent())
         .clampNegativeToZero();
   }
   DISABLE_CFI_PERF LayoutUnit logicalLeftOffsetForContent() const {
     return isHorizontalWritingMode() ? borderLeft() + paddingLeft()
                                      : borderTop() + paddingTop();
   }
   LayoutUnit logicalRightOffsetForContent() const {
@@ skipping 270 matching lines @@
   // TODO(lunalu): Temporary in order to ensure compatibility with existing
   // layout test results.
   virtual void adjustChildDebugRect(LayoutRect&) const {}
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutBlock, isLayoutBlock());
 
 }  // namespace blink
 
 #endif  // LayoutBlock_h