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

third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp

 /*
  * Copyright (C) 2011 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 219 matching lines @@
     if (Platform::current()->themeEngine()) {
       Platform::current()->themeEngine()->getOverlayScrollbarStyle(&style);
     }
     theme = new ScrollbarThemeOverlay(
         style.thumbThickness, style.scrollbarMargin,
         ScrollbarThemeOverlay::DisallowHitTest, Color(style.color));
   }
   return *theme;
 }
 
+bool ScrollbarThemeOverlay::usesNinePatchThumbResource() const {
+  WebThemeEngine* engine = Platform::current()->themeEngine();
+  if (!engine)
+    return false;
+
+  // Thumb orientation doesn't matter here.
+  return engine->supportsNinePatch(WebThemeEngine::PartScrollbarVerticalThumb);
+}
+
+IntSize ScrollbarThemeOverlay::ninePatchThumbCanvasSize(
+    const ScrollbarThemeClient& scrollbar) const {
+  DCHECK(usesNinePatchThumbResource());
+
+  WebThemeEngine::Part part = WebThemeEngine::PartScrollbarHorizontalThumb;
+  if (scrollbar.orientation() == VerticalScrollbar)
+    part = WebThemeEngine::PartScrollbarVerticalThumb;
+
+  DCHECK(Platform::current()->themeEngine());
+  return Platform::current()->themeEngine()->ninePatchCanvasSize(part);
+}
+
+IntRect ScrollbarThemeOverlay::ninePatchThumbAperture(
+    const ScrollbarThemeClient& scrollbar) const {
+  DCHECK(usesNinePatchThumbResource());
+
+  WebThemeEngine::Part part = WebThemeEngine::PartScrollbarHorizontalThumb;
+  if (scrollbar.orientation() == VerticalScrollbar)
+    part = WebThemeEngine::PartScrollbarVerticalThumb;
+
+  DCHECK(Platform::current()->themeEngine());
+  return Platform::current()->themeEngine()->ninePatchAperture(part);
+}
+
 }  // namespace blink