Paint state transition for overlay 9 patch scrollbars

content/child/webthemeengine_impl_default.h

Index: content/child/webthemeengine_impl_default.h
diff --git a/content/child/webthemeengine_impl_default.h b/content/child/webthemeengine_impl_default.h
index 20f88c5e03a811c15a109283e333bd5d148ce966..b757d441b39955ccc186443de7f5bb69c89c3ce1 100644
--- a/content/child/webthemeengine_impl_default.h
+++ b/content/child/webthemeengine_impl_default.h
@@ -19,6 +19,12 @@ class WebThemeEngineImpl : public blink::WebThemeEngine {
       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