Use a direct include of the message_loop header in base/.

base/files/file_path_watcher.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.
 
 // Cross platform methods for FilePathWatcher. See the various platform
 // specific implementation files, too.
 
 #include "base/files/file_path_watcher.h"
 
 #include "base/logging.h"
-#include "base/message_loop.h"
+#include "base/message_loop/message_loop.h"
 
 namespace base {
 
 FilePathWatcher::~FilePathWatcher() {
   impl_->Cancel();
 }
 
 // static
 void FilePathWatcher::CancelWatch(
     const scoped_refptr<PlatformDelegate>& delegate) {
   delegate->CancelOnMessageLoopThread();
 }
 
 FilePathWatcher::PlatformDelegate::PlatformDelegate(): cancelled_(false) {
 }
 
 FilePathWatcher::PlatformDelegate::~PlatformDelegate() {
   DCHECK(is_cancelled());
 }
 
 bool FilePathWatcher::Watch(const FilePath& path,
                             bool recursive,
                             const Callback& callback) {
   DCHECK(path.IsAbsolute());
   return impl_->Watch(path, recursive, callback);
 }
 
 }  // namespace base