Skip screen update when the WebView isn't ready to paint.

chrome/renderer/render_widget.h

 // Copyright (c) 2009 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 CHROME_RENDERER_RENDER_WIDGET_H_
 #define CHROME_RENDERER_RENDER_WIDGET_H_
 #pragma once
 
 #include <vector>
 
@@ skipping 223 matching lines @@
   void SetPendingWindowRect(const WebKit::WebRect& r);
 
   // Called by OnHandleInputEvent() to notify subclasses that a key event was
   // just handled.
   virtual void DidHandleKeyEvent() {}
 
   // Called by OnHandleInputEvent() to notify subclasses that a mouse event was
   // just handled.
   virtual void DidHandleMouseEvent(const WebKit::WebMouseEvent& event) {}
 
+  // Used to determine wheter does DoDeferredUpdate()
+  // The web page might not be loaded enough to paint.
+  virtual bool IsReadyToPaint() const { return true; }
+
   // Routing ID that allows us to communicate to the parent browser process
   // RenderWidgetHost. When MSG_ROUTING_NONE, no messages may be sent.
   int32 routing_id_;
 
   // We are responsible for destroying this object via its Close method.
   WebKit::WebWidget* webwidget_;
 
   // Set to the ID of the view that initiated creating this view, if any. When
   // the view was initiated by the browser (the common case), this will be
   // MSG_ROUTING_NONE. This is used in determining ownership when opening
@@ skipping 88 matching lines @@
   // Indicates if the next sequence of Char events should be suppressed or not.
   bool suppress_next_char_events_;
 
   // Set to true if painting to the window is handled by the GPU process.
   bool is_gpu_rendering_active_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidget);
 };
 
 #endif  // CHROME_RENDERER_RENDER_WIDGET_H_