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

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index b15f6b8b2780dc2e93a1f94464b15e470c701660..c6d1eb2f9e7db2da5ebb2f9518c0dc76297e4346 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -783,6 +783,10 @@ void RenderWidgetCompositor::BeginMainFrame(const cc::BeginFrameArgs& args) {
   widget_->webwidget()->beginFrame(web_begin_frame_args);
 }
 
+void RenderWidgetCompositor::BeginMainFrameNotExpectedSoon() {
+  compositor_deps_->GetRendererScheduler()->BeginFrameNotExpectedSoon();
+}
+
 void RenderWidgetCompositor::Layout() {
   widget_->webwidget()->layout();