[VSync Queue] Plug touch ack to gesture events and flush vsync queue if necessary

content/browser/renderer_host/input/touch_event_queue.h

 // Copyright 2013 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_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 94 matching lines @@
   // Sets whether the current site has a mobile friendly viewport. This
   // determines which ack timeout delay will be used for *future* touch events.
   // The default assumption is that the site is *not* mobile-optimized.
   virtual void SetIsMobileOptimizedSite(bool mobile_optimized_site) = 0;
 
   // Whether ack timeout behavior is supported and enabled for the current site.
   virtual bool IsAckTimeoutEnabled() const = 0;
 
   virtual bool Empty() const WARN_UNUSED_RESULT = 0;
 
+  virtual bool SendTouchEventsAsync() const = 0;
+
  protected:
   virtual void SendTouchCancelEventForTouchEvent(
       const TouchEventWithLatencyInfo& event_to_cancel) = 0;
 
   // Empties the queue of touch events. This may result in any number of gesture
   // events being sent to the renderer.
   virtual void FlushQueue() = 0;
   virtual void UpdateTouchConsumerStates(const blink::WebTouchEvent& event,
                                          InputEventAckState ack_result) = 0;
 
  private:
   friend class TouchTimeoutHandler;
 
   DISALLOW_COPY_AND_ASSIGN(TouchEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_