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

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 0f48cb205dda2d31116c2cc9ea61a9832e7302e9..c571008dbedd5984c43ab6d8d476e82f5cd85b7b 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -226,6 +226,10 @@ void LayerTreeHost::DidBeginMainFrame() {
   client_->DidBeginMainFrame();
 }
 
+void LayerTreeHost::BeginMainFrameNoLongerRequired() {
+  client_->BeginMainFrameNoLongerRequired();
+}
+
 void LayerTreeHost::BeginMainFrame(const BeginFrameArgs& args) {
   inside_begin_main_frame_ = true;
   client_->BeginMainFrame(args);