Add a BeginMainFrame fallback to MainThreadEventQueue.

content/renderer/input/main_thread_event_queue.h

 // Copyright 2016 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 CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_
 #define CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_
 
 #include <deque>
 #include "base/feature_list.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 100 matching lines @@
                          InputEventAckState ack_result,
                          uint32_t touch_event_id);
 
   void SendEventToMainThread(const blink::WebInputEvent* event,
                              const ui::LatencyInfo& latency,
                              InputEventDispatchType original_dispatch_type);
 
   bool IsRafAlignedInputDisabled() const;
   bool IsRafAlignedEvent(
       const std::unique_ptr<MainThreadEventQueueTask>& item) const;
+  void RafFallbackTimerFired();
 
   friend class QueuedWebInputEvent;
   friend class MainThreadEventQueueTest;
   friend class MainThreadEventQueueInitializationTest;
   MainThreadEventQueueClient* client_;
   bool last_touch_start_forced_nonblocking_due_to_fling_;
   bool enable_fling_passive_listener_flag_;
   bool enable_non_blocking_due_to_main_thread_responsiveness_flag_;
   base::TimeDelta main_thread_responsiveness_threshold_;
   bool handle_raf_aligned_touch_input_;
@@ skipping 11 matching lines @@
     bool sent_post_task_;
     base::TimeTicks last_async_touch_move_timestamp_;
   };
 
   // Lock used to serialize |shared_state_|.
   base::Lock shared_state_lock_;
   SharedState shared_state_;
 
   scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
   blink::scheduler::RendererScheduler* renderer_scheduler_;
+  base::OneShotTimer raf_fallback_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(MainThreadEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_