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

ui/compositor/compositor.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_COMPOSITOR_COMPOSITOR_H_
 #define UI_COMPOSITOR_COMPOSITOR_H_
 
 #include <string>
 
 #include "base/containers/hash_tables.h"
@@ skipping 225 matching lines @@
   // Signals swap has completed.
   void OnSwapBuffersComplete();
 
   // Signals swap has aborted (e.g. lost context).
   void OnSwapBuffersAborted();
 
   // LayerTreeHostClient implementation.
   void WillBeginMainFrame() override {}
   void DidBeginMainFrame() override {}
   void BeginMainFrame(const cc::BeginFrameArgs& args) override;
+  void BeginMainFrameNotExpectedSoon() override;
   void Layout() override;
   void ApplyViewportDeltas(const gfx::Vector2dF& inner_delta,
                            const gfx::Vector2dF& outer_delta,
                            const gfx::Vector2dF& elastic_overscroll_delta,
                            float page_scale,
                            float top_controls_delta) override {}
   void ApplyViewportDeltas(const gfx::Vector2d& scroll_delta,
                            float page_scale,
                            float top_controls_delta) override {}
   void RequestNewOutputSurface() override;
@@ skipping 74 matching lines @@
   LayerAnimatorCollection layer_animator_collection_;
 
   base::WeakPtrFactory<Compositor> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Compositor);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_COMPOSITOR_H_