Move FilePathWatcher to base/files.

content/common/file_path_watcher/file_path_watcher_stub.cc

-// Copyright (c) 2011 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.
-
-// This file exists for Unix systems which don't have the inotify headers, and
-// thus cannot build file_watcher_inotify.cc
-
-#include "chrome/common/file_path_watcher/file_path_watcher.h"
-
-class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate {
- public:
-  virtual bool Watch(const FilePath& path,
-                     FileWatcher::Delegate* delegate,
-                     base::MessageLoopProxy*) OVERRIDE {
-    return false;
-  }
-};
-
-FilePathWatcher::FilePathWatcher() {
-  impl_ = new FilePathWatcherImpl();
-}