Add basic support to dump pixel results

content/shell/layout_test_controller.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_SHELL_LAYOUT_TEST_CONTROLLER_H_
 #define CONTENT_SHELL_LAYOUT_TEST_CONTROLLER_H_
 #pragma once
 
 #include "content/public/renderer/render_view_observer.h"
 
 namespace content {
 
 // This is the renderer side of the layout test controller.
 class LayoutTestController : public RenderViewObserver {
  public:
   explicit LayoutTestController(RenderView* render_view);
   virtual ~LayoutTestController();
 
   // RenderViewObserver implementation.
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
   virtual void DidFinishLoad(WebKit::WebFrame* frame) OVERRIDE;
 
  private:
   // Message handlers.
   void OnCaptureTextDump(bool as_text, bool printing, bool recursive);
+  void OnCaptureImageDump();
 
   DISALLOW_COPY_AND_ASSIGN(LayoutTestController);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_SHELL_LAYOUT_TEST_CONTROLLER_H_