Introduce ChildScheduler as common base interface for WorkerScheduler and RendererScheduler.

content/child/scheduler/null_worker_scheduler.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 "content/child/scheduler/null_worker_scheduler.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "content/child/scheduler/null_idle_task_runner.h"
 
@@ skipping 24 matching lines @@
 
 void NullWorkerScheduler::RemoveTaskObserver(
     base::MessageLoop::TaskObserver* task_observer) {
   base::MessageLoop::current()->RemoveTaskObserver(task_observer);
 }
 
 bool NullWorkerScheduler::CanExceedIdleDeadlineIfRequired() const {
   return false;
 }
 
+bool NullWorkerScheduler::ShouldYieldForHighPriorityWork() {
+  return false;
+}
+
 void NullWorkerScheduler::Init() {
 }
 
 void NullWorkerScheduler::Shutdown() {
 }
 
 }  // namespace content