Introduce a hash_of_hashes dictionary.

chrome/browser/prefs/pref_hash_store_impl.h

 // Copyright 2013 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_HASH_STORE_IMPL_H_
 #define CHROME_BROWSER_PREFS_PREF_HASH_STORE_IMPL_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 28 matching lines @@
   // Registers required local state preferences.
   static void RegisterPrefs(PrefRegistrySimple* registry);
 
   // PrefHashStore implementation.
   virtual ValueState CheckValue(const std::string& path,
                                 const base::Value* value) const OVERRIDE;
   virtual void StoreHash(const std::string& path,
                          const base::Value* value) OVERRIDE;
 
  private:
+  // Returns true if the dictionary of hashes stored for |hash_store_id_| is
+  // trusted (which implies unknown values can be trusted as newly tracked
+  // values).
+  bool IsHashDictionaryTrusted() const;
+
   std::string hash_store_id_;
   PrefHashCalculator pref_hash_calculator_;
   PrefService* local_state_;
+  bool initial_hashes_dictionary_trusted_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefHashStoreImpl);
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_HASH_STORE_IMPL_H_