GPU process clients can perform a "shallow" finish.

cc/output/delegating_renderer.h

 // Copyright 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 CC_OUTPUT_DELEGATING_RENDERER_H_
 #define CC_OUTPUT_DELEGATING_RENDERER_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/base/cc_export.h"
 #include "cc/output/compositor_frame.h"
@@ skipping 12 matching lines @@
       OutputSurface* output_surface,
       ResourceProvider* resource_provider);
   virtual ~DelegatingRenderer();
 
   virtual const RendererCapabilities& Capabilities() const OVERRIDE;
 
   virtual bool CanReadPixels() const OVERRIDE;
 
   virtual void DrawFrame(RenderPassList* render_passes_in_draw_order) OVERRIDE;
 
-  virtual void Finish() OVERRIDE {}
+  //virtual void Finish() OVERRIDE {}
 
   virtual void SwapBuffers() OVERRIDE;
   virtual void ReceiveSwapBuffersAck(const CompositorFrameAck&) OVERRIDE;
 
   virtual void GetFramebufferPixels(void* pixels, gfx::Rect rect) OVERRIDE;
 
   virtual bool IsContextLost() OVERRIDE;
 
   virtual void SetVisible(bool visible) OVERRIDE;
 
@@ skipping 12 matching lines @@
   RendererCapabilities capabilities_;
   CompositorFrame frame_for_swap_buffers_;
   bool visible_;
 
   DISALLOW_COPY_AND_ASSIGN(DelegatingRenderer);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_DELEGATING_RENDERER_H_