cc: Make async readback path use async glRreadPixels.

cc/resources/resource_provider.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/resources/resource_provider.h"
 
 #include <limits.h>
 
 #include "base/debug/alias.h"
 #include "base/hash_tables.h"
@@ skipping 423 matching lines @@
   texture_uploader_->ReleaseCachedQueries();
 }
 
 void ResourceProvider::Flush() {
   DCHECK(thread_checker_.CalledOnValidThread());
   WebGraphicsContext3D* context3d = output_surface_->context3d();
   if (context3d)
     context3d->flush();
 }
 
+void ResourceProvider::Finish() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  WebGraphicsContext3D* context3d = output_surface_->context3d();
+  if (context3d)
+    context3d->finish();
+}
+
 bool ResourceProvider::ShallowFlushIfSupported() {
   DCHECK(thread_checker_.CalledOnValidThread());
   WebGraphicsContext3D* context3d = output_surface_->context3d();
   if (!context3d || !use_shallow_flush_)
     return false;
 
   context3d->shallowFlushCHROMIUM();
   return true;
 }
 
@@ skipping 770 matching lines @@
 void ResourceProvider::EnableReadLockFences(ResourceProvider::ResourceId id,
                                             bool enable) {
   DCHECK(thread_checker_.CalledOnValidThread());
   ResourceMap::iterator it = resources_.find(id);
   CHECK(it != resources_.end());
   Resource* resource = &it->second;
   resource->enable_read_lock_fences = enable;
 }
 
 }  // namespace cc