Add a Restore() method to ValueStore and make StorageAPI use it

chrome/browser/extensions/api/storage/weak_unlimited_settings_storage.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 CHROME_BROWSER_EXTENSIONS_API_STORAGE_WEAK_UNLIMITED_SETTINGS_STORAGE_H_
 #define CHROME_BROWSER_EXTENSIONS_API_STORAGE_WEAK_UNLIMITED_SETTINGS_STORAGE_H_
 
 #include "base/compiler_specific.h"
 #include "chrome/browser/value_store/value_store.h"
 
@@ skipping 18 matching lines @@
   virtual ReadResult Get() OVERRIDE;
   virtual WriteResult Set(
       WriteOptions options,
       const std::string& key,
       const base::Value& value) OVERRIDE;
   virtual WriteResult Set(
       WriteOptions options, const base::DictionaryValue& values) OVERRIDE;
   virtual WriteResult Remove(const std::string& key) OVERRIDE;
   virtual WriteResult Remove(const std::vector<std::string>& keys) OVERRIDE;
   virtual WriteResult Clear() OVERRIDE;
+  virtual bool Restore() OVERRIDE;
+  virtual bool RestoreKey(const std::string& key) OVERRIDE;
 
  private:
   // The delegate storage area, NOT OWNED.
   ValueStore* const delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(WeakUnlimitedSettingsStorage);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_STORAGE_WEAK_UNLIMITED_SETTINGS_STORAGE_H_