Stop checking that FilePathWatcher is used from a MessageLoopForIO.

base/files/file_path_watcher_linux.cc

Index: base/files/file_path_watcher_linux.cc
diff --git a/base/files/file_path_watcher_linux.cc b/base/files/file_path_watcher_linux.cc
index 3b0ff6236ec81fe4b41705e2b2c3ea3c2aa07896..bf17cde45f7036aea326d33190b478eb3d1df8d2 100644
--- a/base/files/file_path_watcher_linux.cc
+++ b/base/files/file_path_watcher_linux.cc
@@ -335,7 +335,7 @@ void FilePathWatcherImpl::OnFilePathChanged(InotifyReader::Watch fired_watch,
     return;
   }
 
-  DCHECK(MessageLoopForIO::current());
+  DCHECK(task_runner()->BelongsToCurrentThread());
   DCHECK(HasValidWatchVector());
 
   // Used below to avoid multiple recursive updates.
@@ -420,7 +420,6 @@ 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;