Support single-threaded impl-side painting

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 cba427ebad4ec63920f4fdb428bf88e5a93435b4..62b8b60c9dadfd1acd97a18bbd686b13e9db8870 100644
--- a/cc/resources/gpu_raster_worker_pool.cc
+++ b/cc/resources/gpu_raster_worker_pool.cc
@@ -183,6 +183,10 @@ void GpuRasterWorkerPool::ScheduleTasks(RasterTaskQueue* queue) {
             raster_finished_tasks_);
 }
 
+void GpuRasterWorkerPool::WaitForTasksToFinishRunning() {
+  task_graph_runner_->WaitForTasksToFinishRunning(namespace_token_);

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

This doesn't really make sense. It will block on current thread for all tasks to
run on current thread. It's guaranteed to deadlock.

NOTREACHED() or NOTIMPLEMENTED() would be better but I think we should avoid
that too if possible. See my cc/resources/rasterizer.h comment.

[enne (OOO), 2014/10/27 20:23:24]

I'm happy to change this if this is not right, but this is what you directly
suggested to me to do.

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