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

ui/views/view_unittest.cc

 // Copyright (c) 2012 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 "ui/views/view.h"
 
 #include <stddef.h>
 
 #include <map>
 #include <memory>
@@ skipping 4547 matching lines @@
                         State state,
                         const ExtraParams& extra) const override {
     return gfx::Size();
   }
   void Paint(cc::PaintCanvas* canvas,
              Part part,
              State state,
              const gfx::Rect& rect,
              const ExtraParams& extra) const override {}
 
+  bool SupportsNinePatch(Part part) const override { return false; }
+  gfx::Size GetNinePatchCanvasSize(Part part) const override {
+    return gfx::Size();
+  }
+  gfx::Rect GetNinePatchAperture(Part part) const override {
+    return gfx::Rect();
+  }
+
  private:
   DISALLOW_COPY_AND_ASSIGN(TestNativeTheme);
 };
 
 // Creates and adds a new child view to |parent| that has a layer.
 void AddViewWithChildLayer(View* parent) {
   View* child = new View;
   child->SetPaintToLayer();
   parent->AddChildView(child);
 }
@@ skipping 284 matching lines @@
   std::unique_ptr<View> view = NewView();
   std::unique_ptr<View> child_view = NewView();
   std::unique_ptr<View> child_view2 = NewView();
   view->AddChildView(child_view.get());
   view->AddChildView(child_view2.get());
   view->ReorderChildView(child_view2.get(), 0);
   EXPECT_EQ(child_view2.get(), view_reordered());
 }
 
 }  // namespace views