Add setNeedsLayoutAndFullPaintInvalidation to WebWidget.

public/web/WebWidget.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 74 matching lines @@
     // did{Enter,Exit}FullScreen.
     virtual void willEnterFullScreen() { }
     virtual void didEnterFullScreen() { }
     virtual void willExitFullScreen() { }
     virtual void didExitFullScreen() { }
 
     // Called to update imperative animation state. This should be called before
     // paint, although the client can rate-limit these calls.
     virtual void beginFrame(const WebBeginFrameArgs& frameTime) { }
 
+    // Called when the Widget contents has changed in such a way the layout must be
+    // redone, and any resulting paint invalidations issued.
+    virtual void setNeedsLayoutAndFullPaintInvalidation() { }
+
     // Called to layout the WebWidget. This MUST be called before Paint,
     // and it may result in calls to WebWidgetClient::didInvalidateRect.
     virtual void layout() { }
 
     // Called to paint the rectangular region within the WebWidget
     // onto the specified canvas at (viewPort.x,viewPort.y). You MUST call
     // Layout before calling this method. It is okay to call paint
     // multiple times once layout has been called, assuming no other
     // changes are made to the WebWidget (e.g., once events are
     // processed, it should be assumed that another call to layout is
@@ skipping 164 matching lines @@
     // control what are valid states for top controls and if it should animate.
     virtual void updateTopControlsState(WebTopControlsState constraints, WebTopControlsState current, bool animate) { }
 
 protected:
     ~WebWidget() { }
 };
 
 } // namespace blink
 
 #endif