Delegate touch handler registration logic to the TouchEventQueue

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 <deque>
 #include <map>
 
@@ skipping 40 matching lines @@
   // additional queued touch-events to the renderer.
   void ProcessTouchAck(InputEventAckState ack_result,
                        const ui::LatencyInfo& latency_info);
 
   // When GestureScrollBegin is received, we send a touch cancel to renderer,
   // route all the following touch events directly to client, and ignore the
   // ack for the touch cancel. When Gesture{ScrollEnd,FlingStart} is received,
   // resume the normal flow of sending touch events to the renderer.
   void OnGestureScrollEvent(const GestureEventWithLatencyInfo& gesture_event);
 
-  // Empties the queue of touch events. This may result in any number of gesture
-  // events being sent to the renderer.
-  void FlushQueue();
+  // Notifies the queue whether the renderer has at least one touch handler.
+  void OnHasTouchEventHandlers(bool has_handlers);
 
   // Returns whether the currently pending touch event (waiting ACK) is for
   // a touch start event.
   bool IsPendingAckTouchStart() const;
 
   // Sets whether a delayed touch ack will cancel and flush the current
   // touch sequence.
   void SetAckTimeoutEnabled(bool enabled, size_t ack_timeout_delay_ms);
 
   bool empty() const WARN_UNUSED_RESULT {
     return touch_queue_.empty();
   }
 
   size_t size() const {
     return touch_queue_.size();
   }
 
   bool ack_timeout_enabled() const {
     return ack_timeout_enabled_;
   }
 
+  bool has_handlers() const {
+    return has_handlers_;
+  }
+
  private:
   class TouchTimeoutHandler;
   friend class TouchTimeoutHandler;
   friend class TouchEventQueueTest;
 
   bool HasTimeoutEvent() const;
   bool IsTimeoutRunningForTesting() const;
   const TouchEventWithLatencyInfo& GetLatestEventForTesting() const;
 
+  // Empties the queue of touch events. This may result in any number of gesture
+  // events being sent to the renderer.
+  void FlushQueue();
+
   // Walks the queue, checking each event for |ShouldForwardToRenderer()|.
   // If true, forwards the touch event and stops processing further events.
   // If false, acks the event with |INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS|.
   void TryForwardNextEventToRenderer();
 
   // Pops the touch-event from the top of the queue and sends it to the
   // TouchEventQueueClient. This reduces the size of the queue by one.
   void PopTouchEventToClient(InputEventAckState ack_result,
                              const ui::LatencyInfo& renderer_latency_info);
 
@@ skipping 15 matching lines @@
 
   // Used to defer touch forwarding when ack dispatch triggers |QueueEvent()|.
   // If not NULL, |dispatching_touch_ack_| is the touch event of which the ack
   // is being dispatched.
   CoalescedWebTouchEvent* dispatching_touch_ack_;
 
   // Used to prevent touch timeout scheduling if we receive a synchronous
   // ack after forwarding a touch event to the client.
   bool dispatching_touch_;
 
+  // Whether there are any registered touch handlers. Defaults to false.
+  bool has_handlers_;
+
   // Don't send touch events to the renderer while scrolling.
-  bool no_touch_to_renderer_;
+  bool scroll_in_progress_;

[tdresser, 2014/01/09 21:14:32]

Good rename.

 
   // Whether an event in the current (multi)touch sequence was consumed by the
   // renderer.  The touch timeout will never be activated when this is true.
   bool renderer_is_consuming_touch_gesture_;
 
   // Optional handler for timed-out touch event acks, disabled by default.
   bool ack_timeout_enabled_;
   scoped_ptr<TouchTimeoutHandler> timeout_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(TouchEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_