Clean up vestiges of ScrollView.

Source/web/WebPluginScrollbarImpl.h

 /*
  * Copyright (C) 2012 Google 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 42 matching lines @@
     Scrollbar* scrollbar() { return m_scrollbar.get(); }
 
     // WebScrollbar methods
     virtual bool isOverlay() const override;
     virtual int value() const override;
     virtual WebPoint location() const override;
     virtual WebSize size() const override;
     virtual bool enabled() const override;
     virtual int maximum() const override;
     virtual int totalSize() const override;
-    virtual bool isScrollViewScrollbar() const override;
     virtual bool isScrollableAreaActive() const override;
     virtual void getTickmarks(WebVector<WebRect>& tickmarks) const override;
     virtual WebScrollbar::ScrollbarControlSize controlSize() const override;
     virtual WebScrollbar::ScrollbarPart pressedPart() const override;
     virtual WebScrollbar::ScrollbarPart hoveredPart() const override;
     virtual WebScrollbar::ScrollbarOverlayStyle scrollbarOverlayStyle() const override;
     virtual WebScrollbar::Orientation orientation() const override;
     virtual bool isLeftSideVerticalScrollbar() const override;
     virtual bool isCustomScrollbar() const override;
 
@@ skipping 18 matching lines @@
     ScrollbarGroup* m_group;
     WebPluginScrollbarClient* m_client;
 
     int m_scrollOffset;
     RefPtr<Scrollbar> m_scrollbar;
 };
 
 } // namespace blink
 
 #endif