libaddressinput: Add fallback data for US address validation.

third_party/libaddressinput/chromium/cpp/src/fallback_data_store.h

+// Copyright (C) 2014 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef I18N_ADDRESSINPUT_FALLBACK_DATA_STORE_H_
+#define I18N_ADDRESSINPUT_FALLBACK_DATA_STORE_H_
+
+#include <string>
+
+namespace i18n {
+namespace addressinput {
+
+class FallbackDataStore {
+ public:
+  // Gets default data for |key|. Should only be used as a last resort after
+  // attempts to check the local cache or the webserver have failed.
+  static bool Get(const std::string& key, std::string* data);
+};
+
+}  // namespace addressinput
+}  // namespace i18n
+
+#endif  // I18N_ADDRESSINPUT_FALLBACK_DATA_STORE_H_