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

chrome/browser/extensions/api/storage/settings_test_util.cc

 // 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.
 
 #include "chrome/browser/extensions/api/storage/settings_test_util.h"
 
 #include "base/files/file_path.h"
 #include "chrome/browser/extensions/api/storage/settings_frontend.h"
 #include "chrome/browser/extensions/extension_system_factory.h"
 #include "extensions/common/extension.h"
@@ skipping 144 matching lines @@
   delegate_ = delegate;
 }
 
 ValueStore* ScopedSettingsStorageFactory::Create(
     const base::FilePath& base_path,
     const std::string& extension_id) {
   DCHECK(delegate_.get());
   return delegate_->Create(base_path, extension_id);
 }
 
+void ScopedSettingsStorageFactory::DeleteDatabaseIfExists(
+    const base::FilePath& base_path,
+    const std::string& extension_id) {
+  delegate_->DeleteDatabaseIfExists(base_path, extension_id);
+}
+
 }  // namespace settings_test_util
 
 }  // namespace extensions