Use FSEvents for recursive file watch on Mac

base/files/file_path_watcher_win.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.
 
 #include "base/files/file_path_watcher.h"
 
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
@@ skipping 105 matching lines @@
   if (!message_loop()->BelongsToCurrentThread()) {
     message_loop()->PostTask(FROM_HERE,
                              Bind(&FilePathWatcher::CancelWatch,
                                   make_scoped_refptr(this)));
   } else {
     CancelOnMessageLoopThread();
   }
 }
 
 void FilePathWatcherImpl::CancelOnMessageLoopThread() {
+  DCHECK(message_loop()->BelongsToCurrentThread());
   set_cancelled();
 
   if (handle_ != INVALID_HANDLE_VALUE)
     DestroyWatch();
 
   if (!callback_.is_null()) {
     MessageLoop::current()->RemoveDestructionObserver(this);
     callback_.Reset();
   }
 }
@@ skipping 147 matching lines @@
   handle_ = INVALID_HANDLE_VALUE;
 }
 
 }  // namespace
 
 FilePathWatcher::FilePathWatcher() {
   impl_ = new FilePathWatcherImpl();
 }
 
 }  // namespace base