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

base/threading/thread_local.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.
 
 // WARNING: Thread local storage is a bit tricky to get right.  Please make
 // sure that this is really the proper solution for what you're trying to
 // achieve.  Don't prematurely optimize, most likely you can just use a Lock.
 //
 // These classes implement a wrapper around the platform's TLS storage
 // mechanism.  On construction, they will allocate a TLS slot, and free the
@@ skipping 29 matching lines @@
 //   }
 //
 //   // Return the current MyClass associated with the calling thread, can be
 //   // NULL if there isn't a MyClass associated.
 //   MyClass* MyClass::current() {
 //     return Singleton<ThreadLocalPointer<MyClass> >::get()->Get();
 //   }
 
 #ifndef BASE_THREADING_THREAD_LOCAL_H_
 #define BASE_THREADING_THREAD_LOCAL_H_
-#pragma once
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 
 #if defined(OS_POSIX)
 #include <pthread.h>
 #endif
 
 namespace base {
 
@@ skipping 59 matching lines @@
 
  private:
   ThreadLocalPointer<void> tlp_;
 
   DISALLOW_COPY_AND_ASSIGN(ThreadLocalBoolean);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_THREAD_LOCAL_H_