Expose a SequencedTaskRunner that runs tasks on raster threads.

content/renderer/render_thread_impl.h

Index: content/renderer/render_thread_impl.h
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index 23a8041d9902b8c28c81915c9a5ba84ae055e9e3..80c975edcd61f8d77451ffecacc75aaec96e9772 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -317,6 +317,10 @@ class CONTENT_EXPORT RenderThreadImpl
   // on the renderer's main thread.
   scoped_refptr<base::SingleThreadTaskRunner> GetMediaThreadTaskRunner();
 
+  // Returns a SequencedTaskRunner instance that runs tasks on worker
+  // |compositor_raster_threads_|.
+  scoped_refptr<base::SequencedTaskRunner> GetWorkerSequencedTaskRunner();
+
   // Causes the idle handler to skip sending idle notifications
   // on the two next scheduled calls, so idle notifications are
   // not sent for at least one notification delay.
@@ -566,6 +570,9 @@ class CONTENT_EXPORT RenderThreadImpl
   // Threads used by compositor for rasterization.
   ScopedVector<base::SimpleThread> compositor_raster_threads_;
 
+  // Task runner that runs tasks on |compositor_raster_threads_|.
+  scoped_refptr<base::SequencedTaskRunner> worker_task_runner_;
+
   base::CancelableCallback<void(const IPC::Message&)> main_input_callback_;
   scoped_refptr<IPC::MessageFilter> input_event_filter_;
   scoped_ptr<InputHandlerManager> input_handler_manager_;