cc: Async readback.

cc/trees/layer_tree_host_common.cc

 // Copyright 2011 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/trees/layer_tree_host_common.h"
 
 #include <algorithm>
 
 #include "base/debug/trace_event.h"
 #include "cc/base/math_util.h"
@@ skipping 278 matching lines @@
   //
 
   // The root layer should always have a render_surface.
   if (IsRootLayer(layer))
     return true;
 
   // If we force it.
   if (layer->force_render_surface())
     return true;
 
+  // If we'll make a copy of the layer's contents.
+  if (layer->HasRequestCopyCallback())
+    return true;
+
   // If the layer uses a mask.
   if (layer->mask_layer())
     return true;
 
   // If the layer has a reflection.
   if (layer->replica_layer())
     return true;
 
   // If the layer uses a CSS filter.
   if (!layer->filters().isEmpty() || !layer->background_filters().isEmpty() ||
@@ skipping 1405 matching lines @@
   // At this point, we think the point does hit the touch event handler region
   // on the layer, but we need to walk up the parents to ensure that the layer
   // was not clipped in such a way that the hit point actually should not hit
   // the layer.
   if (PointIsClippedBySurfaceOrClipRect(screen_space_point, layer_impl))
     return false;
 
   return true;
 }
 }  // namespace cc