Set the unique_event_id when converting from TouchEvent to WebTouchEvent

ui/events/gesture_detection/motion_event.h

 // 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.
 
 #ifndef UI_EVENTS_GESTURE_DETECTION_MOTION_EVENT_H_
 #define UI_EVENTS_GESTURE_DETECTION_MOTION_EVENT_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "ui/events/gesture_detection/gesture_detection_export.h"
@@ skipping 29 matching lines @@
     BUTTON_FORWARD = 1 << 4,
   };
 
   // The implementer promises that |GetPointerId()| will never exceed
   // MAX_POINTER_ID.
   enum { MAX_POINTER_ID = 31, MAX_TOUCH_POINT_COUNT = 16 };
 
   virtual ~MotionEvent() {}
 
   virtual int GetId() const = 0;
+  virtual uint32 GetUniqueId() const = 0;

[jdduke (slow), 2015/03/13 21:48:27]

I don't think we want both an id and a unique id...

[tdresser, 2015/03/16 12:24:12]

We require the id to be stable across multiple events (it's the pointer id of
the first pointer), whereas the unique id is separate per event. We should
probably change the naming here though.

   virtual Action GetAction() const = 0;
   // Only valid if |GetAction()| returns ACTION_POINTER_UP or
   // ACTION_POINTER_DOWN.
   virtual int GetActionIndex() const = 0;
   virtual size_t GetPointerCount() const = 0;
   virtual int GetPointerId(size_t pointer_index) const = 0;
   virtual float GetX(size_t pointer_index) const = 0;
   virtual float GetY(size_t pointer_index) const = 0;
   virtual float GetRawX(size_t pointer_index) const = 0;
   virtual float GetRawY(size_t pointer_index) const = 0;
@@ skipping 44 matching lines @@
   // They guarantee only that the returned type will reflect the same
   // data exposed by the MotionEvent interface; no guarantees are made that the
   // underlying implementation is identical to the source implementation.
   scoped_ptr<MotionEvent> Clone() const;
   scoped_ptr<MotionEvent> Cancel() const;
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_GESTURE_DETECTION_MOTION_EVENT_H_