Allow CopyFromBackingStore to fallback to copying from the renderer side if the accelerated surface…

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index 9485aa8828ef69db3d986761f7a237dbcc8dea42..9025b3a0a3250e7a0743fc8b928b262949878b74 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -10,6 +10,7 @@
 #include <map>
 #include <queue>
 #include <string>
+#include <utility>
 #include <vector>
 
 #include "base/callback.h"
@@ -146,6 +147,10 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   virtual void AddKeyboardListener(KeyboardListener* listener) OVERRIDE;
   virtual void RemoveKeyboardListener(KeyboardListener* listener) OVERRIDE;
   virtual void GetWebScreenInfo(WebKit::WebScreenInfo* result) OVERRIDE;
+  virtual void GetSnapshotFromRenderer(
+      const gfx::Rect& src_subrect,
+      const gfx::Size& dst_size,
+      const base::Callback<void(bool, const SkBitmap&)>& callback) OVERRIDE;
 
   // Notification that the screen info has changed.
   void NotifyScreenInfoChanged();
@@ -602,6 +607,7 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   void OnWindowlessPluginDummyWindowDestroyed(
       gfx::NativeViewId dummy_activation_window);
 #endif
+  void OnSnapshot(bool success, const SkBitmap& bitmap);
 
   // Called (either immediately or asynchronously) after we're done with our
   // BackingStore and can send an ACK to the renderer so it can paint onto it
@@ -857,6 +863,10 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   scoped_ptr<GestureEventFilter> gesture_event_filter_;
   scoped_ptr<OverscrollController> overscroll_controller_;
 
+  typedef std::pair<gfx::Size, base::Callback<void(bool, const SkBitmap&)> >
+      PendingSnapshotInfo;
+  std::queue<PendingSnapshotInfo> pending_snapshots_;
+
 #if defined(OS_WIN)
   std::list<HWND> dummy_windows_for_activation_;
 #endif