Adds the UserInputMonitor implementation for Mac.

media/base/user_input_monitor_mac.mm

Index: media/base/user_input_monitor_mac.mm
diff --git a/media/base/user_input_monitor_mac.mm b/media/base/user_input_monitor_mac.mm
deleted file mode 100644
index 4ffad42a72d9b479d1611e4a10fea96ae41e0e5d..0000000000000000000000000000000000000000
--- a/media/base/user_input_monitor_mac.mm
+++ /dev/null
@@ -1,16 +0,0 @@
-// Copyright 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 "media/base/user_input_monitor.h"
-
-namespace media {
-
-// TODO(jiayl): add the implementation.
-scoped_ptr<UserInputMonitor> UserInputMonitor::Create(
-    const scoped_refptr<base::SingleThreadTaskRunner>& input_task_runner,
-    const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner) {
-  return scoped_ptr<UserInputMonitor>();
-}
-
-}  // namespace media