Revert of Don't refcount tracking id -> slot id mapping.

ui/events/ozone/events_ozone.cc

 // Copyright (c) 2013 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.
 
 #include "ui/events/ozone/events_ozone.h"
 
 #include "ui/events/event.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/event_utils.h"
 
@@ skipping 68 matching lines @@
   return event->offset();
 }
 
 base::NativeEvent CopyNativeEvent(const base::NativeEvent& event) {
   return NULL;
 }
 
 void ReleaseCopiedNativeEvent(const base::NativeEvent& event) {
 }
 
+void IncrementTouchIdRefCount(const base::NativeEvent& event) {
+}
+
 void ClearTouchIdIfReleased(const base::NativeEvent& xev) {
 }
 
 int GetTouchId(const base::NativeEvent& native_event) {
   const ui::TouchEvent* event =
       static_cast<const ui::TouchEvent*>(native_event);
   DCHECK(event->IsTouchEvent());
   return event->touch_id();
 }
 
@@ skipping 93 matching lines @@
     callback.Run(&touch_event);
   } else if (native_ui_event->IsScrollEvent()) {
     ui::ScrollEvent scroll_event(native_event);
     callback.Run(&scroll_event);
   } else {
     NOTREACHED();
   }
 }
 
 }  // namespace ui