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

base/mac/foundation_util.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 BASE_MAC_FOUNDATION_UTIL_H_
 #define BASE_MAC_FOUNDATION_UTIL_H_
-#pragma once
 
 #include <CoreFoundation/CoreFoundation.h>
 
 #include <string>
 #include <vector>
 
 #include "base/base_export.h"
 #include "base/logging.h"
 #include "base/mac/scoped_cftyperef.h"
 
@@ skipping 311 matching lines @@
 // by using the NSToCFCast methods above.
 // e.g. LOG(INFO) << base::mac::NSToCFCast(@"foo");
 // Operator << can not be overloaded for ObjectiveC types as the compiler
 // can not distinguish between overloads for id with overloads for void*.
 BASE_EXPORT extern std::ostream& operator<<(std::ostream& o,
                                             const CFErrorRef err);
 BASE_EXPORT extern std::ostream& operator<<(std::ostream& o,
                                             const CFStringRef str);
 
 #endif  // BASE_MAC_FOUNDATION_UTIL_H_