cc: Async readback.

cc/output/direct_renderer.cc

Index: cc/output/direct_renderer.cc
diff --git a/cc/output/direct_renderer.cc b/cc/output/direct_renderer.cc
index ae8ff9b336335b4fc05bf32acf993de2fe891976..bb8449bcb8cf6bcf8088ed60fc8bb5c6ad6dac8c 100644
--- a/cc/output/direct_renderer.cc
+++ b/cc/output/direct_renderer.cc
@@ -192,9 +192,19 @@ void DirectRenderer::DrawFrame(RenderPassList* render_passes_in_draw_order) {
       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)
+  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());
+    }
+  }
   FinishDrawingFrame(&frame);
 
   render_passes_in_draw_order->clear();