GPU process clients can perform a "shallow" finish.

cc/output/gl_renderer.h

 // Copyright 2010 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_GL_RENDERER_H_
 #define CC_OUTPUT_GL_RENDERER_H_
 
 #include "base/cancelable_callback.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/scoped_ptr_vector.h"
@@ skipping 39 matching lines @@
 
   virtual ~GLRenderer();
 
   virtual const RendererCapabilities& Capabilities() const OVERRIDE;
 
   WebKit::WebGraphicsContext3D* Context();
 
   virtual void ViewportChanged() OVERRIDE;
 
   // Waits for rendering to finish.
-  virtual void Finish() OVERRIDE;
+  //virtual void Finish() OVERRIDE;
 
   virtual void DoNoOp() OVERRIDE;
   virtual void SwapBuffers() OVERRIDE;
 
   virtual void GetFramebufferPixels(void* pixels, gfx::Rect rect) OVERRIDE;
 
   virtual bool IsContextLost() OVERRIDE;
 
   virtual void SetVisible(bool visible) OVERRIDE;
 
@@ skipping 377 matching lines @@
 #if DEBUG_GL_CALLS && !defined(NDEBUG)
 #define GLC(context, x)                                                        \
   (x, GLRenderer::DebugGLCall(&* context, #x, __FILE__, __LINE__))
 #else
 #define GLC(context, x) (x)
 #endif
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_GL_RENDERER_H_