Remove #pragma once. Just from base/ for now.

base/win/object_watcher.h

 // 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.
 
 #ifndef BASE_WIN_OBJECT_WATCHER_H_
 #define BASE_WIN_OBJECT_WATCHER_H_
-#pragma once
 
 #include <windows.h>
 
 #include "base/base_export.h"
 #include "base/callback.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop.h"
 
 namespace base {
 namespace win {
@@ skipping 75 matching lines @@
   HANDLE wait_object_;        // Returned by RegisterWaitForSingleObject
   MessageLoop* origin_loop_;  // Used to get back to the origin thread
 
   DISALLOW_COPY_AND_ASSIGN(ObjectWatcher);
 };
 
 }  // namespace win
 }  // namespace base
 
 #endif  // BASE_OBJECT_WATCHER_H_