[WebView] Add a new flushVisualState API to AwContents.

content/browser/frame_host/render_frame_host_impl.h

Index: content/browser/frame_host/render_frame_host_impl.h
diff --git a/content/browser/frame_host/render_frame_host_impl.h b/content/browser/frame_host/render_frame_host_impl.h
index 7b40b9da8db2ce29171cdd0deb5eb32f3fcfcf0d..7b8d0c4909ceb96f6cfb042a422630dd48845a9d 100644
--- a/content/browser/frame_host/render_frame_host_impl.h
+++ b/content/browser/frame_host/render_frame_host_impl.h
@@ -131,6 +131,8 @@ class CONTENT_EXPORT RenderFrameHostImpl
   RenderViewHost* GetRenderViewHost() override;
   ServiceRegistry* GetServiceRegistry() override;
   void ActivateFindInPageResultForAccessibility(int request_id) override;
+  void FlushVisualState(
+      const FlushVisualStateResultCallback& callback) override;
 
   // IPC::Sender
   bool Send(IPC::Message* msg) override;
@@ -440,6 +442,7 @@ class CONTENT_EXPORT RenderFrameHostImpl
   void OnSwapOutACK();
   void OnContextMenu(const ContextMenuParams& params);
   void OnJavaScriptExecuteResponse(int id, const base::ListValue& result);
+  void OnFlushVisualStateResponse(int id);
   void OnRunJavaScriptMessage(const base::string16& message,
                               const base::string16& default_prompt,
                               const GURL& frame_url,
@@ -545,6 +548,7 @@ class CONTENT_EXPORT RenderFrameHostImpl
   // The mapping of pending JavaScript calls created by
   // ExecuteJavaScript and their corresponding callbacks.
   std::map<int, JavaScriptResultCallback> javascript_callbacks_;
+  std::map<int, FlushVisualStateResultCallback> flush_visual_state_callbacks_;
 
   int routing_id_;