RenderWidget's scheduleComposite should return a bool. (true iff a prompt composite will come).

content/renderer/render_widget.h

 // Copyright (c) 2012 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_RENDERER_RENDER_WIDGET_H_
 #define CONTENT_RENDERER_RENDER_WIDGET_H_
 #pragma once
 
 #include <deque>
 #include <vector>
@@ skipping 104 matching lines @@
   // WebKit::WebWidgetClient
   virtual void willBeginCompositorFrame();
   virtual void didInvalidateRect(const WebKit::WebRect&);
   virtual void didScrollRect(int dx, int dy, const WebKit::WebRect& clipRect);
   virtual void didAutoResize(const WebKit::WebSize& new_size);
   virtual void didActivateCompositor(int input_handler_identifier);
   virtual void didDeactivateCompositor();
   virtual void didBecomeReadyForAdditionalInput();
   virtual void didCommitAndDrawCompositorFrame();
   virtual void didCompleteSwapBuffers();
+#if defined(WEBWIDGETCLIENT_SCHEDULECOMPOSITE_RETURNS_BOOL)
+  virtual bool scheduleComposite();
+#else
   virtual void scheduleComposite();
+#endif
   virtual void scheduleAnimation();
   virtual void didFocus();
   virtual void didBlur();
   virtual void didChangeCursor(const WebKit::WebCursorInfo&);
   virtual void closeWidgetSoon();
   virtual void show(WebKit::WebNavigationPolicy);
   virtual void runModal() {}
   virtual WebKit::WebRect windowRect();
   virtual void setToolTipText(const WebKit::WebString& text,
                               WebKit::WebTextDirection hint);
@@ skipping 382 matching lines @@
   // Set to true if we should invert all pixels.
   bool invert_;
 
   // The Skia paint object for inverting.
   scoped_ptr<SkPaint> invert_paint_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidget);
 };
 
 #endif  // CONTENT_RENDERER_RENDER_WIDGET_H_