Generate thumbnails in the browser process.

chrome/browser/renderer_host/render_widget_host.h

Index: chrome/browser/renderer_host/render_widget_host.h
diff --git a/chrome/browser/renderer_host/render_widget_host.h b/chrome/browser/renderer_host/render_widget_host.h
index 2eda8cdd36364429f41f0af79b7690281a4bf4dc..bfefefa1481944172fb3c45089b785328297d408 100644
--- a/chrome/browser/renderer_host/render_widget_host.h
+++ b/chrome/browser/renderer_host/render_widget_host.h
@@ -393,6 +393,8 @@ class RenderWidgetHost : public IPC::Channel::Listener,
   // Activate deferred plugin handles.
   void ActivateDeferredPluginHandles();
 
+  const gfx::Size& last_scroll_offset() const { return last_scroll_offset_; }
+
  protected:
   // Internal implementation of the public Forward*Event() methods.
   void ForwardInputEvent(const WebKit::WebInputEvent& input_event,
@@ -665,6 +667,9 @@ class RenderWidgetHost : public IPC::Channel::Listener,
 
   std::vector<gfx::PluginWindowHandle> deferred_plugin_handles_;
 
+  // The last scroll offset of the render widget.
+  gfx::Size last_scroll_offset_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHost);
 };