Don't send touch move to renderer while scrolling

content/browser/renderer_host/touch_event_queue.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 CONTENT_BROWSER_RENDERER_HOST_TOUCH_EVENT_QUEUE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_TOUCH_EVENT_QUEUE_H_
 
 #include <deque>
 #include <map>
 
@@ skipping 19 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);
 
+  // On receiving the first GestureScrollUpdate, flushes any touch events in
+  // the queue to view, sends a touch cancel event to the renderer immediately,
+  // and then resets the event queue so as not to process the acked touch cancel
+  // event.
+  void OnGestureScrollStart();
+
   // Empties the queue of touch events. This may result in any number of gesture
   // events being sent to the renderer.
   void FlushQueue();
 
   // Resets all internal state. This does not trigger any touch or gesture
   // events to be sent.
   void Reset();
 
   // Returns whether the event-queue is empty.
   bool empty() const WARN_UNUSED_RESULT {
@@ skipping 11 matching lines @@
   void PopTouchEventToView(InputEventAckState ack_result);
 
   bool ShouldForwardToRenderer(const WebKit::WebTouchEvent& event) const;
 
   // The RenderWidgetHost that owns this event-queue.
   RenderWidgetHostImpl* render_widget_host_;
 
   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_;
 
   DISALLOW_COPY_AND_ASSIGN(TouchEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_TOUCH_EVENT_QUEUE_H_