Convert Aura to use ui::Event.

ui/aura/event_mac.mm

Index: ui/aura/event_mac.mm
===================================================================
--- ui/aura/event_mac.mm	(revision 150582)
+++ ui/aura/event_mac.mm	(working copy)
@@ -1,15 +0,0 @@
-// Copyright (c) 2012 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.
-
-#import <AppKit/NSEvent.h>
-
-#include "ui/aura/event_mac.h"
-
-namespace aura {
-
-base::NativeEvent CopyNativeEvent(const base::NativeEvent& event) {
-  return [NSEvent eventWithCGEvent:[event CGEvent]];
-}
-
-}  // namespace aura