Make sure send one WebTouchEvent ack per ui::TouchEvent

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 164 matching lines @@
     case ET_TOUCH_RELEASED:
       if (GetPointerCount() == 1) {
         set_action(ACTION_UP);
       } else {
         set_action(ACTION_POINTER_UP);
         set_action_index(GetIndexFromId(touch.touch_id()));
       }
       break;
     case ET_TOUCH_CANCELLED:
       set_action(ACTION_CANCEL);
+      set_action_index(GetIndexFromId(touch.touch_id()));

[tdresser, 2015/05/04 20:41:10]

This causes us to deviate from the Android implementation
(http://developer.android.com/reference/android/view/MotionEvent.html#getActio...),
which isn't ideal.

I think this change won't work correctly on Android.

[jdduke (slow), 2015/05/04 20:46:43]

Yeah, I'd prefer that we not overload the meaning of this property. In
particular, on Android, we get batched movement, so for multitouch all pointers
can move for a single event.

       break;
     case ET_TOUCH_MOVED:
       set_action(ACTION_MOVE);
+      set_action_index(GetIndexFromId(touch.touch_id()));
       break;
     default:
       NOTREACHED();
       break;
   }
 }
 
 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