cc: Make async readback path use async glRreadPixels.

cc/output/direct_renderer.cc

 // 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.
 
 #include "cc/output/direct_renderer.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/debug/trace_event.h"
@@ skipping 175 matching lines @@
   const RenderPass* root_render_pass = render_passes_in_draw_order->back();
   DCHECK(root_render_pass);
 
   DrawingFrame frame;
   frame.root_render_pass = root_render_pass;
   frame.root_damage_rect =
       Capabilities().using_partial_swap && client_->AllowPartialSwap() ?
       root_render_pass->damage_rect : root_render_pass->output_rect;
   frame.root_damage_rect.Intersect(gfx::Rect(ViewportSize()));
 
-  std::vector<base::Closure> copy_callbacks;
-
   BeginDrawingFrame(&frame);
   for (size_t i = 0; i < render_passes_in_draw_order->size(); ++i) {
     DrawRenderPass(&frame, render_passes_in_draw_order->at(i));
 
     const RenderPass* pass = frame.current_render_pass;
-    for (size_t i = 0; i < pass->copy_callbacks.size(); ++i) {
-      scoped_ptr<SkBitmap> bitmap(new SkBitmap);
-      CopyCurrentRenderPassToBitmap(&frame, bitmap.get());
-      pass->copy_callbacks[i].Run(bitmap.Pass());
-    }
+    for (size_t i = 0; i < pass->copy_callbacks.size(); ++i)
+      CopyCurrentRenderPassToBitmap(&frame, pass->copy_callbacks[i]);
   }
   FinishDrawingFrame(&frame);
 
   render_passes_in_draw_order->clear();
 }
 
 gfx::RectF DirectRenderer::ComputeScissorRectForRenderPass(
     const DrawingFrame* frame) {
   gfx::RectF render_pass_scissor = frame->current_render_pass->output_rect;
 
@@ skipping 132 matching lines @@
 gfx::Size DirectRenderer::RenderPassTextureSize(const RenderPass* render_pass) {
   return render_pass->output_rect.size();
 }
 
 // static
 GLenum DirectRenderer::RenderPassTextureFormat(const RenderPass* render_pass) {
   return GL_RGBA;
 }
 
 }  // namespace cc