cc: Make async readback path use async glRreadPixels.

cc/output/direct_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_DIRECT_RENDERER_H_
 #define CC_OUTPUT_DIRECT_RENDERER_H_
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "cc/base/cc_export.h"
 #include "cc/output/renderer.h"
 #include "cc/resources/resource_provider.h"
 #include "cc/resources/scoped_resource.h"
 
 namespace cc {
 
 class ResourceProvider;
 
 // This is the base class for code shared between the GL and software
@@ skipping 83 matching lines @@
   virtual void SetDrawViewportSize(gfx::Size viewport_size) = 0;
   virtual void SetScissorTestRect(gfx::Rect scissor_rect) = 0;
   virtual void ClearFramebuffer(DrawingFrame* frame) = 0;
   virtual void DoDrawQuad(DrawingFrame* frame, const DrawQuad* quad) = 0;
   virtual void BeginDrawingFrame(DrawingFrame* frame) = 0;
   virtual void FinishDrawingFrame(DrawingFrame* frame) = 0;
   virtual void FinishDrawingQuadList();
   virtual bool FlippedFramebuffer() const = 0;
   virtual void EnsureScissorTestEnabled() = 0;
   virtual void EnsureScissorTestDisabled() = 0;
-  virtual void CopyCurrentRenderPassToBitmap(DrawingFrame* frame,
-                                             SkBitmap* bitmap) = 0;
+
+  typedef base::Callback<void(scoped_ptr<SkBitmap>)>
+      CopyRenderPassCallback;
+  virtual void CopyCurrentRenderPassToBitmap(
+      DrawingFrame* frame,
+      const CopyRenderPassCallback& callback) = 0;
 
   ScopedPtrHashMap<RenderPass::Id, CachedResource> render_pass_textures_;
   ResourceProvider* resource_provider_;
 
  private:
   gfx::Vector2d enlarge_pass_texture_amount_;
 
   DISALLOW_COPY_AND_ASSIGN(DirectRenderer);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_DIRECT_RENDERER_H_