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

cc/resources/pixel_buffer_raster_worker_pool.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/pixel_buffer_raster_worker_pool.h"
 
 #include <algorithm>
 
 #include "base/containers/stack_container.h"
 #include "base/debug/trace_event.h"
@@ skipping 243 matching lines @@
     DCHECK_EQ(RasterTaskState::COMPLETED, state_it->type);
 
     std::swap(*state_it, raster_task_states_.back());
     raster_task_states_.pop_back();
 
     task->RunReplyOnOriginThread();
   }
   completed_raster_tasks_.clear();
 }
 
-SkCanvas* PixelBufferRasterWorkerPool::AcquireCanvasForRaster(
+RasterCanvas* PixelBufferRasterWorkerPool::AcquireCanvasForRaster(
     RasterTask* task) {
   DCHECK(std::find_if(raster_task_states_.begin(),
                       raster_task_states_.end(),
                       RasterTaskState::TaskComparator(task)) !=
          raster_task_states_.end());
   resource_provider_->AcquirePixelRasterBuffer(task->resource()->id());
   return resource_provider_->MapPixelRasterBuffer(task->resource()->id());
 }
 
 void PixelBufferRasterWorkerPool::ReleaseCanvasForRaster(RasterTask* task) {
@@ skipping 477 matching lines @@
 void PixelBufferRasterWorkerPool::ThrottleStateAsValueInto(
     base::debug::TracedValue* throttle_state) const {
   throttle_state->SetInteger("bytes_available_for_upload",
                              max_bytes_pending_upload_ - bytes_pending_upload_);
   throttle_state->SetInteger("bytes_pending_upload", bytes_pending_upload_);
   throttle_state->SetInteger("scheduled_raster_task_count",
                              scheduled_raster_task_count_);
 }
 
 }  // namespace cc