Don't send touch move to renderer while scrolling

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 33 matching lines @@
   // queued events (e.g. consecutive touch-move events can be coalesced into a
   // single touch-move event). The event may also be immediately forwarded to
   // the renderer (e.g. when there are no other queued touch event).
   void QueueEvent(const TouchEventWithLatencyInfo& event);
 
   // Notifies the queue that a touch-event has been processed by the renderer.
   // At this point, the queue may send one or more gesture events and/or
   // additional queued touch-events to the renderer.
   void ProcessTouchAck(InputEventAckState ack_result);
 
+  // When scroll starts, we stop forwarding touch events to renderer. When
+  // scroll ends, we flush the queue and send touch end to renderer to release
+  // all existing touches. And we don't want to process the touch end in view,
+  // so we also clear the queue to not process the ack to the touch end.

[sadrul, 2013/08/06 19:34:19]

I think with this patchset, the sequence of events is:
 1. Browser queues up a bunch of events in the queue.
 2. Renderer doesn't prevent-default the touches.
 3. Browser starts sending gesture-scroll events.
 4. The RWHView implementations directly process the subsequent touch-events to
generate more scroll events.
 5. Scroll ends. At this point, the queued touch-move events upto step 3 are
sent to the RWHView. The touch-event is sent to the renderer.

Is this correct? If so, then this is buggy. The events queued up until step 3
needs to be processed by the RWHV before any of the subsequent touches.

+  void OnGestureScrollEnd();
+
+  void ClearQueue();
+
   // Empties the queue of touch events. This may result in any number of gesture
   // events being sent to the renderer.
   void FlushQueue();
 
   // Returns whether the event-queue is empty.
   bool empty() const WARN_UNUSED_RESULT {
     return touch_queue_.empty();
   }
 
  private:
   friend class MockRenderWidgetHost;
 
   CONTENT_EXPORT size_t GetQueueSize() const;
   CONTENT_EXPORT const TouchEventWithLatencyInfo& GetLatestEvent() const;
 
   // 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 PopTouchEventWithAck(InputEventAckState ack_result);
 
   bool ShouldForwardToRenderer(const WebKit::WebTouchEvent& event) const;
 
   // Handles touch event forwarding and ack'ed event dispatch.
   TouchEventQueueClient* client_;
 
   typedef std::deque<CoalescedWebTouchEvent*> TouchQueue;
   TouchQueue touch_queue_;
 
+  TouchEventWithLatencyInfo latest_event_;
+
   // Maintain the ACK status for each touch point.
   typedef std::map<int, InputEventAckState> TouchPointAckStates;
   TouchPointAckStates touch_ack_states_;
 
   // Used to defer touch forwarding when ack dispatch triggers |QueueEvent()|.
   bool dispatching_touch_ack_;
 
   DISALLOW_COPY_AND_ASSIGN(TouchEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EVENT_QUEUE_H_