gpu video: optimize HW video to SW canvas and implement it for WebRTC.

cc/resources/video_resource_updater.cc

 // Copyright 2013 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/resources/video_resource_updater.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
@@ skipping 276 matching lines @@
     DCHECK(plane_resource.mailbox.IsZero());
 
     if (!PlaneResourceMatchesUniqueID(plane_resource, video_frame.get(), 0)) {
       // We need to transfer data from |video_frame| to the plane resource.
       if (!video_renderer_)
         video_renderer_.reset(new media::SkCanvasVideoRenderer);
 
       ResourceProvider::ScopedWriteLockSoftware lock(
           resource_provider_, plane_resource.resource_id);
       SkCanvas canvas(lock.sk_bitmap());
-      video_renderer_->Copy(video_frame, &canvas);
+      video_renderer_->Copy(video_frame, &canvas, media::Context3D());

[dshwang, 2015/01/21 13:40:32]

this is software path, so canvas and video_frame are always backed by software 

[danakj, 2015/02/10 17:48:12]

how about making this a comment in the code?

       SetPlaneResourceUniqueId(video_frame.get(), 0, &plane_resource);
     }
 
     external_resources.software_resources.push_back(plane_resource.resource_id);
     external_resources.software_release_callback =
         base::Bind(&RecycleResource, AsWeakPtr(), plane_resource.resource_id);
     external_resources.type = VideoFrameExternalResources::SOFTWARE_RESOURCE;
     return external_resources;
   }
 
@@ skipping 113 matching lines @@
     resource_it->ref_count = 0;
     updater->DeleteResource(resource_it);
     return;
   }
 
   --resource_it->ref_count;
   DCHECK_GE(resource_it->ref_count, 0);
 }
 
 }  // namespace cc