Remove #pragma once from sync

sync/syncable/in_memory_directory_backing_store.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.
 
 #ifndef SYNC_SYNCABLE_IN_MEMORY_DIRECTORY_BACKING_STORE_H_
 #define SYNC_SYNCABLE_IN_MEMORY_DIRECTORY_BACKING_STORE_H_
-#pragma once
 
 #include "sync/syncable/directory_backing_store.h"
 
 namespace syncer {
 namespace syncable {
 
 // This implementation of DirectoryBackingStore is used in tests that do not
 // require us to write to a file.  An in-memory sqlite database is much faster
 // than an on-disk database, so this can result in significant speedups in our
 // unit tests.
 //
 // An InMemoryDirectoryBackingStore cannot load data from existing databases.
 // When an InMemoryDirectoryBackingStore is destroyed, all data stored in this
 // database is lost.  If these limitations are a problem for you, consider using
 // TestDirectoryBackingStore.
 class InMemoryDirectoryBackingStore : public DirectoryBackingStore {
  public:
   explicit InMemoryDirectoryBackingStore(const std::string& dir_name);
   virtual DirOpenResult Load(
       MetahandlesIndex* entry_bucket,
       Directory::KernelLoadInfo* kernel_load_info) OVERRIDE;
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif  // SYNC_SYNCABLE_IN_MEMORY_DIRECTORY_BACKING_STORE_H_