Don't call into ScrollView from Scrollbar.

Source/platform/scroll/ScrollView.h

 /*
  * Copyright (C) 2004, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Holger Hans Peter Freyther
  *
  * 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
@@ skipping 54 matching lines @@
 
     // Functions for child manipulation and inspection.
     const HashSet<RefPtr<Widget> >* children() const { return &m_children; }
     virtual void addChild(PassRefPtr<Widget>);
     virtual void removeChild(Widget*);
 
     // If the scroll view does not use a native widget, then it will have cross-platform Scrollbars. These functions
     // can be used to obtain those scrollbars.
     virtual Scrollbar* horizontalScrollbar() const OVERRIDE { return m_horizontalScrollbar.get(); }
     virtual Scrollbar* verticalScrollbar() const OVERRIDE { return m_verticalScrollbar.get(); }
-    bool isScrollViewScrollbar(const Widget* child) const { return horizontalScrollbar() == child || verticalScrollbar() == child; }
+    virtual bool isScrollViewScrollbar(const Widget* child) const OVERRIDE { return horizontalScrollbar() == child || verticalScrollbar() == child; }
 
     void positionScrollbarLayers();
 
     // Functions for setting and retrieving the scrolling mode in each axis (horizontal/vertical). The mode has values of
     // AlwaysOff, AlwaysOn, and Auto. AlwaysOff means never show a scrollbar, AlwaysOn means always show a scrollbar.
     // Auto means show a scrollbar only when one is needed.
     // Note that for platforms with native widgets, these modes are considered advisory. In other words the underlying native
     // widget may choose not to honor the requested modes.
     void setScrollbarModes(ScrollbarMode horizontalMode, ScrollbarMode verticalMode, bool horizontalLock = false, bool verticalLock = false);
     void setHorizontalScrollbarMode(ScrollbarMode mode, bool lock = false) { setScrollbarModes(mode, verticalScrollbarMode(), lock, verticalScrollbarLock()); }
@@ skipping 194 matching lines @@
     // Subclassed by FrameView to check the writing-mode of the document.
     virtual bool isVerticalDocument() const { return true; }
     virtual bool isFlippedDocument() const { return false; }
 
     enum ComputeScrollbarExistenceOption {
         FirstPass,
         Incremental
     };
     void computeScrollbarExistence(bool& newHasHorizontalScrollbar, bool& newHasVerticalScrollbar, const IntSize& docSize, ComputeScrollbarExistenceOption = FirstPass) const;
     void updateScrollbarGeometry();
+    IntRect adjustScrollbarRectForResizer(const IntRect&, Scrollbar*);
 
     // Called to update the scrollbars to accurately reflect the state of the view.
     void updateScrollbars(const IntSize& desiredOffset);
 
     IntSize excludeScrollbars(const IntSize&) const;
 
     class InUpdateScrollbarsScope {
     public:
         explicit InUpdateScrollbarsScope(ScrollView* view)
             : m_scope(view->m_inUpdateScrollbars, true)
@@ skipping 44 matching lines @@
 
     void calculateOverhangAreasForPainting(IntRect& horizontalOverhangRect, IntRect& verticalOverhangRect);
     void updateOverhangAreas();
 }; // class ScrollView
 
 DEFINE_TYPE_CASTS(ScrollView, Widget, widget, widget->isScrollView(), widget.isScrollView());
 
 } // namespace blink
 
 #endif // ScrollView_h