Set the unique_event_id when converting from TouchEvent to WebTouchEvent

ui/events/gestures/motion_event_aura.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_UI_MOTION_EVENT_H_
 #define UI_EVENTS_GESTURE_DETECTION_UI_MOTION_EVENT_H_
 
 #include <map>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "ui/events/event.h"
 #include "ui/events/events_export.h"
 #include "ui/events/gesture_detection/motion_event_generic.h"
 
 namespace ui {
 
 // Implementation of MotionEvent which takes a stream of ui::TouchEvents.
 class EVENTS_EXPORT MotionEventAura : public MotionEventGeneric {
  public:
   MotionEventAura();
   ~MotionEventAura() override;
 
   // MotionEventGeneric:
-  int GetId() const override;
   int GetSourceDeviceId(size_t pointer_index) const override;
 
   // Returns true iff the touch was valid.
   bool OnTouch(const TouchEvent& touch);
 
   // We can't cleanup removed touch points immediately upon receipt of a
   // TouchCancel or TouchRelease, as the MotionEvent needs to be able to report
   // information about those touch events. Once the MotionEvent has been
   // processed, we call CleanupRemovedTouchPoints to do the required
   // book-keeping.
   void CleanupRemovedTouchPoints(const TouchEvent& event);
 
  private:
   void AddTouch(const TouchEvent& touch);
   void UpdateTouch(const TouchEvent& touch);
   void UpdateCachedAction(const TouchEvent& touch);
   int GetIndexFromId(int id) const;
 
   DISALLOW_COPY_AND_ASSIGN(MotionEventAura);
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_GESTURE_DETECTION_UI_MOTION_EVENT_H_