Redirect the MessageLoop's task runner to the renderer scheduler

components/scheduler/child/task_queue_manager.cc

Index: components/scheduler/child/task_queue_manager.cc
diff --git a/components/scheduler/child/task_queue_manager.cc b/components/scheduler/child/task_queue_manager.cc
index 71b2d86e3ddc8e98d27c8ab39cc180e83618cd30..043049ac7b90a64a2532e0713bf392ec6db491d9 100644
--- a/components/scheduler/child/task_queue_manager.cc
+++ b/components/scheduler/child/task_queue_manager.cc
@@ -510,6 +510,9 @@ TaskQueueManager::TaskQueueManager(
       base::Bind(&TaskQueueManager::DoWork, weak_factory_.GetWeakPtr(), true);
   do_work_from_other_thread_closure_ =
       base::Bind(&TaskQueueManager::DoWork, weak_factory_.GetWeakPtr(), false);
+
+  if (task_queue_count)
+    main_task_runner->SetDefaultTaskRunner(Queue(0));

[alex clarke (OOO till 29th), 2015/07/08 13:30:53]

It's currently true that task #0 is the default queue.  Do we want to formalize
that somehow, or to pass the default task queue index in as a parameter?

[Sami, 2015/07/08 18:45:07]

Good point. I thought about this a bit an realized that the task queue manager
doesn't really even need to know about the default task runner -- it's more of a
helper thing. Because of this I've now added a new interface called
SchedulerTaskRunnerDelegate which basically adds the default task runner
overriding on top of NestableSingleThreadTaskRunner. Unfortunately this makes
the patch a little bigger, but I think the refactoring makes sense especially if
we want to move TQM to base some day.

 }
 
 TaskQueueManager::~TaskQueueManager() {