[cc]: Add a BeginMainFrameNotExpectedSoon signal and route it to the RendererScheduler.

content/test/fake_renderer_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/test/fake_renderer_scheduler.h"
 
 namespace content {
 
 FakeRendererScheduler::FakeRendererScheduler() {
 }
@@ skipping 17 matching lines @@
 }
 
 scoped_refptr<SingleThreadIdleTaskRunner>
 FakeRendererScheduler::IdleTaskRunner() {
   return nullptr;
 }
 
 void FakeRendererScheduler::WillBeginFrame(const cc::BeginFrameArgs& args) {
 }
 
+void FakeRendererScheduler::BeginFrameNotExpectedSoon() {
+}
+
 void FakeRendererScheduler::DidCommitFrameToCompositor() {
 }
 
 void FakeRendererScheduler::DidReceiveInputEventOnCompositorThread(
     const blink::WebInputEvent& web_input_event) {
 }
 
 void FakeRendererScheduler::DidAnimateForInputOnCompositorThread() {
 }
 
 bool FakeRendererScheduler::IsHighPriorityWorkAnticipated() {
   return false;
 }
 
 bool FakeRendererScheduler::ShouldYieldForHighPriorityWork() {
   return false;
 }
 
 void FakeRendererScheduler::Shutdown() {
 }
 
 }  // namespace content