This adds in the ability for Chrome to generate windows with snapshots of all...

chrome/browser/renderer_host/render_widget_host_painting_observer.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_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_PAINTING_OBSERVER_H_
 #define CHROME_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_PAINTING_OBSERVER_H_
 
+#include "app/surface/transport_dib.h"
+
 class BackingStore;
 class RenderWidgetHost;
+class SkBitmap;
+
+namespace gfx {
+class Size;
+}
 
 // This class can be used to observe painting events for a RenderWidgetHost.
 // Its primary goal in Chrome is to allow thumbnails to be generated.
 class RenderWidgetHostPaintingObserver {
  public:
   // Indicates the RenderWidgetHost is about to destroy the backing store. The
   // backing store will still be valid when this call is made.
   virtual void WidgetWillDestroyBackingStore(RenderWidgetHost* widget,
                                              BackingStore* backing_store) = 0;
 
   // Indicates that the RenderWidgetHost just updated the backing store.
   virtual void WidgetDidUpdateBackingStore(RenderWidgetHost* widget) = 0;
+
+  // This notifies the painting observer that a PaintAtSizeACK was
+  // received.
+  virtual void WidgetDidReceivePaintAtSizeAck(
+      RenderWidgetHost* widget,
+      const TransportDIB::Handle& dib_handle,
+      const gfx::Size& size) = 0;
 };
 
 #endif  // CHROME_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_PAINTING_OBSERVER_H_