Support single-threaded impl-side painting

cc/resources/pixel_buffer_raster_worker_pool.cc

Index: cc/resources/pixel_buffer_raster_worker_pool.cc
diff --git a/cc/resources/pixel_buffer_raster_worker_pool.cc b/cc/resources/pixel_buffer_raster_worker_pool.cc
index 9ad641ad474496ba283ce4168e9bc1a25edf993e..965bc8d3696fddfdfd5955da55346992173ba12d 100644
--- a/cc/resources/pixel_buffer_raster_worker_pool.cc
+++ b/cc/resources/pixel_buffer_raster_worker_pool.cc
@@ -287,6 +287,10 @@ void PixelBufferRasterWorkerPool::ScheduleTasks(RasterTaskQueue* queue) {
       "cc", "ScheduledTasks", this, StateName(), "state", StateAsValue());
 }
 
+void PixelBufferRasterWorkerPool::WaitForTasksToFinishRunning() {
+  task_graph_runner_->WaitForTasksToFinishRunning(namespace_token_);

[reveman, 2014/10/27 19:15:49]

Note that this doesn't do what is expected. It will only wait for currently
scheduled tasks to finish running and not take throttling into account.

+}
+
 void PixelBufferRasterWorkerPool::CheckForCompletedTasks() {
   TRACE_EVENT0("cc", "PixelBufferRasterWorkerPool::CheckForCompletedTasks");