Adds a SHUTDOWN_TASK_QUEUE and a PreShutdown api to the scheduler.

content/test/fake_renderer_scheduler.cc

Index: content/test/fake_renderer_scheduler.cc
diff --git a/content/test/fake_renderer_scheduler.cc b/content/test/fake_renderer_scheduler.cc
index 1424706f3854e0704080b7961a64d9dfb97b9395..aa8e38b5680924e6c4cf6d143c5bd3f285591f05 100644
--- a/content/test/fake_renderer_scheduler.cc
+++ b/content/test/fake_renderer_scheduler.cc
@@ -37,6 +37,11 @@ FakeRendererScheduler::TimerTaskRunner() {
   return nullptr;
 }
 
+scoped_refptr<base::SingleThreadTaskRunner>
+FakeRendererScheduler::ShutdownTaskRunner() {
+  return nullptr;
+}
+
 void FakeRendererScheduler::WillBeginFrame(const cc::BeginFrameArgs& args) {
 }
 
@@ -79,6 +84,9 @@ void FakeRendererScheduler::RemoveTaskObserver(
     base::MessageLoop::TaskObserver* task_observer) {
 }
 
+void FakeRendererScheduler::PreShutdown() {
+}
+
 void FakeRendererScheduler::Shutdown() {
 }