Support browser side thumbnailing for GPU composited pages on Windows.

ui/gfx/surface/accelerated_surface_win.h

Index: ui/gfx/surface/accelerated_surface_win.h
diff --git a/ui/gfx/surface/accelerated_surface_win.h b/ui/gfx/surface/accelerated_surface_win.h
index 9b48b363aa9732d35faec468281eaf7333397204..52208d3dae735746364075adabd0b8bb4a71b2c3 100644
--- a/ui/gfx/surface/accelerated_surface_win.h
+++ b/ui/gfx/surface/accelerated_surface_win.h
@@ -32,6 +32,7 @@ class AcceleratedPresenter
       int64 surface_id,
       const base::Callback<void(bool)>& completion_task);
   bool Present(gfx::NativeWindow window);
+  bool CopyTo(const gfx::Size& size, void* buf);
   void Suspend();
   void WaitForPendingTasks();
 
@@ -85,6 +86,12 @@ class SURFACE_EXPORT AcceleratedSurface {
   // Synchronously present a frame with no acknowledgement.
   bool Present(gfx::NativeWindow window);
 
+  // Copies the surface data to |buf|. The image data is transformed so that it
+  // fits in |size|.
+  // Caller must ensure that |buf| is allocated with the size no less than
+  // |4 * size.width() * size.height()| bytes.
+  bool CopyTo(const gfx::Size& size, void* buf);
+
   // Temporarily release resources until a new surface is asynchronously
   // presented. Present will not be able to represent the last surface after
   // calling this and will return false.