Introduce ChildScheduler as common base interface for WorkerScheduler and RendererScheduler.

content/child/scheduler/worker_scheduler_impl.cc

Index: content/child/scheduler/worker_scheduler_impl.cc
diff --git a/content/child/scheduler/worker_scheduler_impl.cc b/content/child/scheduler/worker_scheduler_impl.cc
index 63661db5ea972805e09f8056ac923d42a54f3698..064d03cb4aded8bdcfeda39f478b20a87d157008 100644
--- a/content/child/scheduler/worker_scheduler_impl.cc
+++ b/content/child/scheduler/worker_scheduler_impl.cc
@@ -52,6 +52,11 @@ bool WorkerSchedulerImpl::CanExceedIdleDeadlineIfRequired() const {
   return helper_.CanExceedIdleDeadlineIfRequired();
 }
 
+bool WorkerSchedulerImpl::ShouldYieldForHighPriorityWork() {
+  // We don't consider any work as being high priority on workers.
+  return false;
+}
+
 void WorkerSchedulerImpl::AddTaskObserver(
     base::MessageLoop::TaskObserver* task_observer) {
   DCHECK(initialized_);