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

cc/resources/gpu_raster_worker_pool.cc

Index: cc/resources/gpu_raster_worker_pool.cc
diff --git a/cc/resources/gpu_raster_worker_pool.cc b/cc/resources/gpu_raster_worker_pool.cc
index f38fa7b14a1acb22bcd8004fd4e12d73191d7c97..36d62aad8a195ecdb2cad7f75df0f25d6fd48ee0 100644
--- a/cc/resources/gpu_raster_worker_pool.cc
+++ b/cc/resources/gpu_raster_worker_pool.cc
@@ -148,12 +148,12 @@ void GpuRasterWorkerPool::CheckForCompletedTasks() {
   completed_tasks_.clear();
 }
 
-SkCanvas* GpuRasterWorkerPool::AcquireCanvasForRaster(RasterTask* task) {
-  return resource_provider_->MapGpuRasterBuffer(task->resource()->id());
+RasterBuffer* GpuRasterWorkerPool::AcquireBufferForRaster(RasterTask* task) {
+  return resource_provider_->AcquireGpuRasterBuffer(task->resource()->id());
 }
 
-void GpuRasterWorkerPool::ReleaseCanvasForRaster(RasterTask* task) {
-  resource_provider_->UnmapGpuRasterBuffer(task->resource()->id());
+void GpuRasterWorkerPool::ReleaseBufferForRaster(RasterTask* task) {
+  resource_provider_->ReleaseGpuRasterBuffer(task->resource()->id());
 }
 
 void GpuRasterWorkerPool::OnRasterFinished() {