Set the unique_event_id when converting from TouchEvent to WebTouchEvent

ui/events/gestures/motion_event_aura.cc

Index: ui/events/gestures/motion_event_aura.cc
diff --git a/ui/events/gestures/motion_event_aura.cc b/ui/events/gestures/motion_event_aura.cc
index 174918fedc5a545da380fd2efd3205e36c3e3258..01df3f6042620f5dd945e786f91d93affda7a1db 100644
--- a/ui/events/gestures/motion_event_aura.cc
+++ b/ui/events/gestures/motion_event_aura.cc
@@ -125,15 +125,12 @@ bool MotionEventAura::OnTouch(const TouchEvent& touch) {
   }
 
   UpdateCachedAction(touch);
+  set_unique_event_id(touch.unique_event_id());

[sadrul, 2015/04/23 16:56:23]

For multi-touch motion-events, the 'unique id' of the motion event is going to
change during its lifetime. Is that safe?

[lanwei, 2015/04/24 20:21:09]

For the unique_event_id, we only use it when the gesture recognizer valid the
touch events' acks are associated with the right touch event. Also in our
ongoing CL( Issue 997283002), we use it to check if the ack is from async
touchmove, so it should be safe and we want it to be different every time when
we dispatch them. We have a PointerId which is identical for every touch point.

   set_flags(touch.flags());
   set_event_time(touch.time_stamp() + base::TimeTicks());
   return true;
 }
 
-int MotionEventAura::GetId() const {
-  return GetPointerId(0);
-}
-
 void MotionEventAura::CleanupRemovedTouchPoints(const TouchEvent& event) {
   if (event.type() != ET_TOUCH_RELEASED &&
       event.type() != ET_TOUCH_CANCELLED) {