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

content/child/webthemeengine_impl_default.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/child/webthemeengine_impl_default.h"
 
 #include "build/build_config.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/WebKit/public/platform/WebRect.h"
 #include "third_party/WebKit/public/platform/WebSize.h"
@@ skipping 235 matching lines @@
 
 void WebThemeEngineImpl::getOverlayScrollbarStyle(ScrollbarStyle* style) {
   style->fadeOutDelaySeconds = ui::kOverlayScrollbarFadeOutDelay.InSecondsF();
   style->fadeOutDurationSeconds =
       ui::kOverlayScrollbarFadeOutDuration.InSecondsF();
   // The other fields in this struct are used only on Android to draw solid
   // color scrollbars. On other platforms the scrollbars are painted in
   // NativeTheme so these fields are unused.
 }
 
+bool WebThemeEngineImpl::supportsNinePatch(Part part) const {
+  return ui::NativeTheme::GetInstanceForWeb()->SupportsNinePatch(
+      NativeThemePart(part));
+}
+
+blink::WebSize WebThemeEngineImpl::ninePatchCanvasSize(Part part) const {
+  return ui::NativeTheme::GetInstanceForWeb()->GetNinePatchCanvasSize(
+      NativeThemePart(part));
+}
+
+blink::WebRect WebThemeEngineImpl::ninePatchAperture(Part part) const {
+  return ui::NativeTheme::GetInstanceForWeb()->GetNinePatchAperture(
+      NativeThemePart(part));
+}
+
 #if defined(OS_WIN)
 // static
 void WebThemeEngineImpl::cacheScrollBarMetrics(
     int32_t vertical_scroll_bar_width,
     int32_t horizontal_scroll_bar_height,
     int32_t vertical_arrow_bitmap_height,
     int32_t horizontal_arrow_bitmap_width) {
   g_vertical_scroll_bar_width = vertical_scroll_bar_width;
   g_horizontal_scroll_bar_height = horizontal_scroll_bar_height;
   g_vertical_arrow_bitmap_height = vertical_arrow_bitmap_height;
   g_horizontal_arrow_bitmap_width = horizontal_arrow_bitmap_width;
 }
 #endif
 
 }  // namespace content