Set the unique_event_id when converting from TouchEvent to WebTouchEvent

ui/events/gestures/motion_event_aura.cc

 // Copyright 2014 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.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include "ui/events/gestures/motion_event_aura.h"
 
 #include <cmath>
@@ skipping 107 matching lines @@
       break;
     case ET_TOUCH_MOVED:
       UpdateTouch(touch);
       break;
     default:
       NOTREACHED();
       return false;
   }
 
   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) {
     return;
   }
 
   DCHECK(GetPointerCount());
   int index_to_delete = GetIndexFromId(event.touch_id());
   set_action_index(0);
   pointer(index_to_delete) = pointer(GetPointerCount() - 1);
@@ skipping 49 matching lines @@
 }
 
 int MotionEventAura::GetIndexFromId(int id) const {
   int index = FindPointerIndexOfId(id);
   DCHECK_GE(index, 0);
   DCHECK_LT(index, static_cast<int>(GetPointerCount()));
   return index;
 }
 
 }  // namespace ui