cc: Do bitmap conversion for RasterBuffer in the worker thread.

cc/resources/image_copy_raster_worker_pool.cc

 // Copyright 2014 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/image_copy_raster_worker_pool.h"
 
 #include <algorithm>
 
 #include "base/debug/trace_event.h"
 #include "base/debug/trace_event_argument.h"
@@ skipping 148 matching lines @@
     task->CompleteOnOriginThread(this);
     task->DidComplete();
 
     task->RunReplyOnOriginThread();
   }
   completed_tasks_.clear();
 
   FlushCopies();
 }
 
-SkCanvas* ImageCopyRasterWorkerPool::AcquireCanvasForRaster(RasterTask* task) {
+RasterCanvas* ImageCopyRasterWorkerPool::AcquireCanvasForRaster(
+    RasterTask* task) {
   DCHECK_EQ(task->resource()->format(), resource_pool_->resource_format());
   scoped_ptr<ScopedResource> resource(
       resource_pool_->AcquireResource(task->resource()->size()));
-  SkCanvas* canvas = resource_provider_->MapImageRasterBuffer(resource->id());
+  RasterCanvas* canvas =
+      resource_provider_->MapImageRasterBuffer(resource->id());
   DCHECK(std::find_if(raster_task_states_.begin(),
                       raster_task_states_.end(),
                       RasterTaskState::TaskComparator(task)) ==
          raster_task_states_.end());
   raster_task_states_.push_back(RasterTaskState(task, resource.release()));
   return canvas;
 }
 
 void ImageCopyRasterWorkerPool::ReleaseCanvasForRaster(RasterTask* task) {
   RasterTaskState::Vector::iterator it =
@@ skipping 69 matching lines @@
                             resource_pool_->total_memory_usage_bytes());
   staging_state->SetInteger("pending_copy_count",
                             resource_pool_->total_resource_count() -
                                 resource_pool_->acquired_resource_count());
   staging_state->SetInteger("bytes_pending_copy",
                             resource_pool_->total_memory_usage_bytes() -
                                 resource_pool_->acquired_memory_usage_bytes());
 }
 
 }  // namespace cc