Fix up leak in FilePathWatcherTest and UserStyleSheetTest

content/common/file_path_watcher/file_path_watcher_mac.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 "content/common/file_path_watcher/file_path_watcher.h"
 
 #include <fcntl.h>
 #include <sys/event.h>
 #include <sys/param.h>
 
@@ skipping 456 matching lines @@
 }
 
 void FilePathWatcherImpl::CancelOnMessageLoopThread() {
   DCHECK(MessageLoopForIO::current());
   if (!is_cancelled()) {
     set_cancelled();
     kqueue_watcher_.StopWatchingFileDescriptor();
     CloseFileDescriptor(&kqueue_);
     std::for_each(events_.begin(), events_.end(), ReleaseEvent);
     events_.clear();
-    io_message_loop_.release();
+    io_message_loop_ = NULL;
     MessageLoop::current()->RemoveDestructionObserver(this);
     delegate_ = NULL;
   }
 }
 
 }  // namespace
 
 FilePathWatcher::FilePathWatcher() {
   impl_ = new FilePathWatcherImpl();
 }