Stop checking that FilePathWatcher is used from a MessageLoopForIO.

base/files/file_path_watcher_linux.cc

 // 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.
 
 #include "base/files/file_path_watcher.h"
 
 #include <errno.h>
 #include <stddef.h>
 #include <string.h>
 #include <sys/inotify.h>
@@ skipping 317 matching lines @@
     return;
   }
 
   // Check to see if CancelOnMessageLoopThreadOrInDestructor() has already been
   // called. May happen when code flow reaches here from the PostTask() above.
   if (watches_.empty()) {
     DCHECK(target_.empty());
     return;
   }
 
-  DCHECK(MessageLoopForIO::current());
+  DCHECK(task_runner()->BelongsToCurrentThread());
   DCHECK(HasValidWatchVector());
 
   // Used below to avoid multiple recursive updates.
   bool did_update = false;
 
   // Find the entry in |watches_| that corresponds to |fired_watch|.
   for (size_t i = 0; i < watches_.size(); ++i) {
     const WatchEntry& watch_entry = watches_[i];
     if (fired_watch != watch_entry.watch)
       continue;
@@ skipping 64 matching lines @@
     if (!did_update)
       UpdateRecursiveWatches(fired_watch, is_dir);
     callback_.Run(target_, false /* error */);
   }
 }
 
 bool FilePathWatcherImpl::Watch(const FilePath& path,
                                 bool recursive,
                                 const FilePathWatcher::Callback& callback) {
   DCHECK(target_.empty());
-  DCHECK(MessageLoopForIO::current());
 
   set_task_runner(ThreadTaskRunnerHandle::Get());
   callback_ = callback;
   target_ = path;
   recursive_ = recursive;
 
   std::vector<FilePath::StringType> comps;
   target_.GetComponents(&comps);
   DCHECK(!comps.empty());
   for (size_t i = 1; i < comps.size(); ++i)
@@ skipping 221 matching lines @@
 }
 
 }  // namespace
 
 FilePathWatcher::FilePathWatcher() {
   sequence_checker_.DetachFromSequence();
   impl_ = new FilePathWatcherImpl();
 }
 
 }  // namespace base