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

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

Index: third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp
index 14878b965bced578d4f7f87378289b66d2df1896..d7ab59bef47849e6ecc4c2ef38e8f0751194ee49 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp
@@ -237,4 +237,37 @@ ScrollbarThemeOverlay& ScrollbarThemeOverlay::mobileTheme() {
   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