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

base/test/thread_test_helper.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_TEST_THREAD_TEST_HELPER_H_
 #define BASE_TEST_THREAD_TEST_HELPER_H_
-#pragma once
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop_proxy.h"
 #include "base/synchronization/waitable_event.h"
 
 namespace base {
 
 // Helper class that executes code on a given thread while blocking on the
 // invoking thread. To use, derive from this class and overwrite RunTest. An
@@ skipping 22 matching lines @@
   bool test_result_;
   scoped_refptr<MessageLoopProxy> target_thread_;
   WaitableEvent done_event_;
 
   DISALLOW_COPY_AND_ASSIGN(ThreadTestHelper);
 };
 
 }  // namespace base
 
 #endif  // BASE_TEST_THREAD_TEST_HELPER_H_