ConfigurationPolicyPrefStore refactoring to surface error messages.

chrome/browser/prefs/pref_value_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_PREFS_PREF_VALUE_MAP_H_
 #define CHROME_BROWSER_PREFS_PREF_VALUE_MAP_H_
 #pragma once
 
 #include <map>
 #include <string>
@@ skipping 53 matching lines @@
 
   // Sets the value for |key| to the int |value|.
   void SetInteger(const std::string& key, const int value);
 
   // Compares this value map against |other| and stores all key names that have
   // different values in |differing_keys|. This includes keys that are present
   // only in one of the maps.
   void GetDifferingKeys(const PrefValueMap* other,
                         std::vector<std::string>* differing_keys) const;
 
+  // Copies all entries in |other| to this value map. Overwrites any existing
+  // value if a key already exists in this value map.
+  void MergeFrom(const PrefValueMap* other);
+
  private:
   typedef std::map<std::string, base::Value*> Map;
 
   Map prefs_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefValueMap);
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_VALUE_MAP_H_