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

chrome/browser/extensions/api/storage/leveldb_settings_storage_factory.h

Index: chrome/browser/extensions/api/storage/leveldb_settings_storage_factory.h
diff --git a/chrome/browser/extensions/api/storage/leveldb_settings_storage_factory.h b/chrome/browser/extensions/api/storage/leveldb_settings_storage_factory.h
index e5a211d828fafbdf656dbf7094658f2028d4a488..6dc54cb92ea1d982bddb0786ad57ac3567c3703b 100644
--- a/chrome/browser/extensions/api/storage/leveldb_settings_storage_factory.h
+++ b/chrome/browser/extensions/api/storage/leveldb_settings_storage_factory.h
@@ -15,6 +15,9 @@ class LeveldbSettingsStorageFactory : public SettingsStorageFactory {
   virtual ValueStore* Create(const base::FilePath& base_path,
                              const std::string& extension_id) OVERRIDE;
 
+  virtual void DeleteDatabaseIfExists(const base::FilePath& base_path,
+                                      const std::string& extension_id) OVERRIDE;
+
  private:
   // SettingsStorageFactory is refcounted.
   virtual ~LeveldbSettingsStorageFactory() {}