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

content/renderer/scheduler/renderer_scheduler.h

Index: content/renderer/scheduler/renderer_scheduler.h
diff --git a/content/renderer/scheduler/renderer_scheduler.h b/content/renderer/scheduler/renderer_scheduler.h
index 6b4ecfaceef4fcd45bd998c5d288eed43c650371..0a57339bd9f08f2f4d862079bf73d76edb49c597 100644
--- a/content/renderer/scheduler/renderer_scheduler.h
+++ b/content/renderer/scheduler/renderer_scheduler.h
@@ -36,6 +36,10 @@ class CONTENT_EXPORT RendererScheduler {
   // to resource dispatch, foreground HTML parsing, etc...
   virtual scoped_refptr<base::SingleThreadTaskRunner> LoadingTaskRunner() = 0;
 
+  // Called to notify about the start of an extended period where no frames
+  // need to be drawn. Must be called from the main thread.
+  virtual void BeginFrameNotExpectedSoon() = 0;
+
   // Called to notify about the start of a new frame.  Must be called from the
   // main thread.
   virtual void WillBeginFrame(const cc::BeginFrameArgs& args) = 0;