Remove #pragma once from sync

sync/sessions/sync_session_context.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.
 
 // SyncSessionContext encapsulates the contextual information and engine
 // components specific to a SyncSession. A context is accessible via
 // a SyncSession so that session SyncerCommands and parts of the engine have
 // a convenient way to access other parts. In this way it can be thought of as
 // the surrounding environment for the SyncSession. The components of this
 // environment are either valid or not valid for the entire context lifetime,
 // or they are valid for explicitly scoped periods of time by using Scoped
 // installation utilities found below. This means that the context assumes no
 // ownership whatsoever of any object that was not created by the context
 // itself.
 //
 // It can only be used from the SyncerThread.
 
 #ifndef SYNC_SESSIONS_SYNC_SESSION_CONTEXT_H_
 #define SYNC_SESSIONS_SYNC_SESSION_CONTEXT_H_
-#pragma once
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/time.h"
 #include "sync/engine/sync_engine_event.h"
 #include "sync/engine/syncer_types.h"
 #include "sync/engine/traffic_recorder.h"
 #include "sync/internal_api/public/engine/model_safe_worker.h"
@@ skipping 168 matching lines @@
  private:
   SyncSessionContext* context_;
   ConflictResolver* resolver_;
   DISALLOW_COPY_AND_ASSIGN(ScopedSessionContextConflictResolver);
 };
 
 }  // namespace sessions
 }  // namespace syncer
 
 #endif  // SYNC_SESSIONS_SYNC_SESSION_CONTEXT_H_