Paint state transition for overlay 9 patch scrollbars

content/child/webthemeengine_impl_default.h

 // 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.
 
 #ifndef CONTENT_CHILD_WEBTHEMEENGINE_IMPL_DEFAULT_H_
 #define CONTENT_CHILD_WEBTHEMEENGINE_IMPL_DEFAULT_H_
 
 #include "third_party/WebKit/public/platform/WebThemeEngine.h"
 
 namespace content {
 
 class WebThemeEngineImpl : public blink::WebThemeEngine {
  public:
   // WebThemeEngine methods:
   virtual blink::WebSize getSize(blink::WebThemeEngine::Part);
   virtual void paint(
       blink::WebCanvas* canvas,
       blink::WebThemeEngine::Part part,
       blink::WebThemeEngine::State state,
       const blink::WebRect& rect,
       const blink::WebThemeEngine::ExtraParams* extra_params);
+  virtual void paintStateTransition(blink::WebCanvas* canvas,
+                                    blink::WebThemeEngine::Part part,
+                                    blink::WebThemeEngine::State startState,
+                                    blink::WebThemeEngine::State endState,
+                                    double progress,
+                                    const blink::WebRect& rect);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_WEBTHEMEENGINE_IMPL_DEFAULT_H_