Send touch cancel to renderer when scrolling starts

content/browser/renderer_host/input/touch_event_queue.h

Index: content/browser/renderer_host/input/touch_event_queue.h
diff --git a/content/browser/renderer_host/input/touch_event_queue.h b/content/browser/renderer_host/input/touch_event_queue.h
index d1f4a6180bfdd3049f32e8ba9a8ddb3c851cb5cc..42c0ffb917428a9134d21af9f0f7a2ccb49298ea 100644
--- a/content/browser/renderer_host/input/touch_event_queue.h
+++ b/content/browser/renderer_host/input/touch_event_queue.h
@@ -52,6 +52,12 @@ class TouchEventQueue {
   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 GestureScrollEnd/GestureFlingStart is
+  // received, we resume the normal flow of sending touch events to 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();
@@ -61,10 +67,6 @@ class TouchEventQueue {
     return touch_queue_.empty();
   }
 
-  void set_no_touch_move_to_renderer(bool value) {
-    no_touch_move_to_renderer_ = value;
-  }
-
  private:
   friend class MockRenderWidgetHost;
   friend class ImmediateInputRouterTest;
@@ -95,12 +97,14 @@ class TouchEventQueue {
   TouchPointAckStates touch_ack_states_;
 
   // Used to defer touch forwarding when ack dispatch triggers |QueueEvent()|.
-  bool dispatching_touch_ack_;
-
-  // Don't send touch move events to renderer. This is enabled when the page
-  // is scrolling. This behaviour is currently enabled only on aura behind a
-  // flag.
-  bool no_touch_move_to_renderer_;
+  // If not NULL, |dispatching_touch_ack_| is the touch event of which the ack
+  // is being dispatched.
+  CoalescedWebTouchEvent* dispatching_touch_ack_;
+
+  // Don't send touch events to renderer. This is enabled when the page
+  // is scrolling. This behaviour is currently enabled only on aura behind
+  // a flag.
+  bool no_touch_to_renderer_;
 
   DISALLOW_COPY_AND_ASSIGN(TouchEventQueue);
 };