Make policy errors available to display in about:policy.

chrome/browser/policy/policy_map.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.
 
 #ifndef CHROME_BROWSER_POLICY_POLICY_MAP_H_
 #define CHROME_BROWSER_POLICY_POLICY_MAP_H_
+#pragma once
 
 #include <map>
 
 #include "base/values.h"
 #include "policy/configuration_policy_type.h"
 
 namespace policy {
 
 struct PolicyDefinitionList;
 
@@ skipping 41 matching lines @@
                              const PolicyMapType::value_type& b);
 
   PolicyMapType map_;
 
   DISALLOW_COPY_AND_ASSIGN(PolicyMap);
 };
 
 }  // namespace policy
 
 #endif  // CHROME_BROWSER_POLICY_POLICY_MAP_H_