Correct const accessors in base/values.(h|cc)

chrome/installer/util/google_chrome_distribution.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.
 //
 // This file extends generic BrowserDistribution class to declare Google Chrome
 // specific implementation.
 
 #ifndef CHROME_INSTALLER_UTIL_GOOGLE_CHROME_DISTRIBUTION_H_
 #define CHROME_INSTALLER_UTIL_GOOGLE_CHROME_DISTRIBUTION_H_
 
@@ skipping 115 matching lines @@
 
   // Extracts uninstall metrics from the given JSON value.
   virtual bool ExtractUninstallMetrics(const base::DictionaryValue& root,
                                        string16* uninstall_metrics);
 
   // Given a DictionaryValue containing a set of uninstall metrics,
   // this builds a URL parameter list of all the contained metrics.
   // Returns true if at least one uninstall metric was found in
   // uninstall_metrics_dict, false otherwise.
   virtual bool BuildUninstallMetricsString(
-      base::DictionaryValue* uninstall_metrics_dict, string16* metrics);
+      const base::DictionaryValue* uninstall_metrics_dict, string16* metrics);
 
   // The product ID for Google Update.
   string16 product_guid_;
 };
 
 #endif  // CHROME_INSTALLER_UTIL_GOOGLE_CHROME_DISTRIBUTION_H_