Use nine-patch resource for drawing Aura overlay scrollbar thumb.

third_party/WebKit/public/platform/WebScrollbarThemePainter.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
@@ skipping 10 matching lines @@
  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef WebScrollbarThemePainter_h
 #define WebScrollbarThemePainter_h
 
 #include "public/platform/WebCanvas.h"
 #include "public/platform/WebPrivatePtr.h"
+#include "public/platform/WebRect.h"
+#include "public/platform/WebSize.h"
 
 namespace blink {
 
 class ScrollbarTheme;
 class Scrollbar;
 class WebScrollbar;
-struct WebRect;
 
 class WebScrollbarThemePainter {
  public:
   WebScrollbarThemePainter() : m_theme(0), m_deviceScaleFactor(1.0) {}
   WebScrollbarThemePainter(const WebScrollbarThemePainter& painter) {
     assign(painter);
   }
   virtual ~WebScrollbarThemePainter() { reset(); }
   WebScrollbarThemePainter& operator=(const WebScrollbarThemePainter& painter) {
     assign(painter);
@@ skipping 16 matching lines @@
   BLINK_PLATFORM_EXPORT void paintTickmarks(WebCanvas*, const WebRect&);
   BLINK_PLATFORM_EXPORT void paintThumb(WebCanvas*, const WebRect&);
 
   // This opacity is applied on top of the content that is painted for the
   // thumb.
   BLINK_PLATFORM_EXPORT float thumbOpacity() const;
 
   BLINK_PLATFORM_EXPORT bool trackNeedsRepaint() const;
   BLINK_PLATFORM_EXPORT bool thumbNeedsRepaint() const;
 
+  BLINK_PLATFORM_EXPORT bool usesNinePatchThumbResource() const;
+
 #if INSIDE_BLINK
   BLINK_PLATFORM_EXPORT WebScrollbarThemePainter(ScrollbarTheme&,
                                                  Scrollbar&,
                                                  float deviceScaleFactor);
 #endif
 
  private:
   // The theme is not owned by this class. It is assumed that the theme is a
   // static pointer and its lifetime is essentially infinite. The functions
   // called from the painter may not be thread-safe, so all calls must be made
   // from the same thread that it is created on.
   ScrollbarTheme* m_theme;
 
   // It is assumed that the constructor of this paint object is responsible
   // for the lifetime of this scrollbar. The painter has to use the real
   // scrollbar (and not a WebScrollbar wrapper) due to static_casts for
   // LayoutScrollbar and pointer-based HashMap lookups for Lion scrollbars.
   WebPrivatePtr<Scrollbar> m_scrollbar;
 
   float m_deviceScaleFactor;
 };
 
 }  // namespace blink
 
 #endif