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

base/threading/post_task_and_reply_impl.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.
 
 // This file contains the implementation shared by
 // MessageLoopProxy::PostTaskAndReply and WorkerPool::PostTaskAndReply.
 
 #ifndef BASE_THREADING_POST_TASK_AND_REPLY_IMPL_H_
 #define BASE_THREADING_POST_TASK_AND_REPLY_IMPL_H_
-#pragma once
 
 #include "base/callback_forward.h"
 #include "base/location.h"
 
 namespace base {
 namespace internal {
 
 // Inherit from this in a class that implements PostTask appropriately
 // for sending to a destination thread.
 //
@@ skipping 13 matching lines @@
 
  private:
   virtual bool PostTask(const tracked_objects::Location& from_here,
                         const Closure& task) = 0;
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_THREADING_POST_TASK_AND_REPLY_IMPL_H_