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

third_party/WebKit/Source/platform/exported/WebScrollbarThemeGeometryNative.cpp

 /*
  * 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 64 matching lines @@
   return m_theme.forwardButtonRect(WebScrollbarThemeClientImpl(*scrollbar),
                                    ForwardButtonStartPart, false);
 }
 
 WebRect WebScrollbarThemeGeometryNative::forwardButtonEndRect(
     WebScrollbar* scrollbar) {
   return m_theme.forwardButtonRect(WebScrollbarThemeClientImpl(*scrollbar),
                                    ForwardButtonEndPart, false);
 }
 
+WebSize WebScrollbarThemeGeometryNative::ninePatchThumbCanvasSize(
+    WebScrollbar* scrollbar) {
+  DCHECK(m_theme.usesNinePatchThumbResource());
+  return m_theme.ninePatchThumbCanvasSize(
+      WebScrollbarThemeClientImpl(*scrollbar));
+}
+
+WebRect WebScrollbarThemeGeometryNative::ninePatchThumbAperture(
+    WebScrollbar* scrollbar) {
+  DCHECK(m_theme.usesNinePatchThumbResource());
+  return m_theme.ninePatchThumbAperture(
+      WebScrollbarThemeClientImpl(*scrollbar));
+}
+
 }  // namespace blink