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

base/memory/mru_cache.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.
 
 // This file contains a template for a Most Recently Used cache that allows
 // constant-time access to items using a key, but easy identification of the
 // least-recently-used items for removal.  Each key can only be associated with
 // one payload item at a time.
 //
 // The key object will be stored twice, so it should support efficient copying.
 //
 // NOTE: While all operations are O(1), this code is written for
 // legibility rather than optimality. If future profiling identifies this as
 // a bottleneck, there is room for smaller values of 1 in the O(1). :]
 
 #ifndef BASE_MEMORY_MRU_CACHE_H_
 #define BASE_MEMORY_MRU_CACHE_H_
-#pragma once
 
 #include <list>
 #include <map>
 #include <utility>
 
 #include "base/basictypes.h"
 #include "base/hash_tables.h"
 #include "base/logging.h"
 
 namespace base {
@@ skipping 268 matching lines @@
   virtual ~HashingMRUCache() {
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(HashingMRUCache);
 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_MRU_CACHE_H_