Remove #pragma once from sync

sync/internal_api/public/util/weak_handle.h

 // Copyright (c) 2012 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.
 
 // Weak handles provides a way to refer to weak pointers from another
 // thread.  This is useful because it is not safe to reference a weak
 // pointer from a thread other than the thread on which it was
 // created.
 //
 // Weak handles can be passed across threads, so for example, you can
@@ skipping 28 matching lines @@
 //
 //   /* Will always be called on the correct thread, and only if this
 //      object hasn't been destroyed. */
 //   void OnIOStart() { DCHECK(CalledOnValidThread(); ... }
 //   void OnIOEvent(IOEvent e) { DCHECK(CalledOnValidThread(); ... }
 //   void OnIOError(IOError err) { DCHECK(CalledOnValidThread(); ... }
 // };
 
 #ifndef SYNC_UTIL_WEAK_HANDLE_H_
 #define SYNC_UTIL_WEAK_HANDLE_H_
-#pragma once
 
 #include <cstddef>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/callback_forward.h"
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "base/location.h"
 #include "base/logging.h"
@@ skipping 310 matching lines @@
 
 // Makes a WeakHandle from a WeakPtr.
 template <typename T>
 WeakHandle<T> MakeWeakHandle(const base::WeakPtr<T>& ptr) {
   return WeakHandle<T>(ptr);
 }
 
 }  // namespace syncer
 
 #endif  // SYNC_UTIL_WEAK_HANDLE_H_