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

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index 770d9b0abd4bbaad26d8e1fd9b7434ab0e3a7c75..9b2289a5f400260a06e8f382ed051f04a8ffbd3d 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -678,6 +678,10 @@ void SingleThreadProxy::ScheduledActionSendBeginMainFrame() {
                  weak_factory_.GetWeakPtr()));
 }
 
+void SingleThreadProxy::SendBeginMainFrameNotExpectedSoon() {
+  layer_tree_host_->BeginMainFrameNotExpectedSoon();
+}
+
 void SingleThreadProxy::BeginMainFrame() {
   if (defer_commits_) {
     TRACE_EVENT_INSTANT0("cc", "EarlyOut_DeferCommit",