compositor worker: Use a WebThread for the compositor thread.

components/scheduler/renderer/renderer_scheduler_impl.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/scheduler/renderer/renderer_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/debug/stack_trace.h"
 #include "base/logging.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 136 matching lines @@
 
 void RendererSchedulerImpl::Shutdown() {
   helper_.Shutdown();
   MainThreadOnly().was_shutdown = true;
 }
 
 scoped_ptr<blink::WebThread> RendererSchedulerImpl::CreateMainThread() {
   return make_scoped_ptr(new WebThreadImplForRendererScheduler(this));
 }
 
-scoped_refptr<TaskQueue> RendererSchedulerImpl::DefaultTaskRunner() {
+scoped_refptr<base::SingleThreadTaskRunner>
+RendererSchedulerImpl::DefaultTaskRunner() {
   return helper_.DefaultTaskRunner();
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
 RendererSchedulerImpl::CompositorTaskRunner() {
   helper_.CheckOnValidThread();
   return compositor_task_runner_;
 }
 
 scoped_refptr<SingleThreadIdleTaskRunner>
@@ skipping 913 matching lines @@
 
 void RendererSchedulerImpl::UnregisterTimeDomain(TimeDomain* time_domain) {
   helper_.UnregisterTimeDomain(time_domain);
 }
 
 base::TickClock* RendererSchedulerImpl::tick_clock() const {
   return helper_.scheduler_tqm_delegate().get();
 }
 
 }  // namespace scheduler