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

cc/scheduler/scheduler.h

Index: cc/scheduler/scheduler.h
diff --git a/cc/scheduler/scheduler.h b/cc/scheduler/scheduler.h
index 82f305a298411b272b55b6fa3df42a26c0a3917f..370ac25b6c4bf44a5f50db03c7147bae17192a92 100644
--- a/cc/scheduler/scheduler.h
+++ b/cc/scheduler/scheduler.h
@@ -49,6 +49,7 @@ class SchedulerClient {
   virtual base::TimeDelta CommitToActivateDurationEstimate() = 0;
   virtual void DidBeginImplFrameDeadline() = 0;
   virtual void SendBeginFramesToChildren(const BeginFrameArgs& args) = 0;
+  virtual void SendBeginMainFrameNotExpectedSoon() = 0;

[Sami, 2015/02/11 15:28:24]

Could you add a scheduler unit test for this? Just a basic one for now -- we can
add the tricky corner cases later as we run into them :)

[rmcilroy, 2015/02/13 16:32:45]

Done.  Also update all the other tests to expect these signals where
appropriate.

 
  protected:
   virtual ~SchedulerClient() {}