WIP: Locale class: toLanguageTag(), parse() factory constructor, getters

lib/ui/hash_codes.dart

@@ -119,3 +119,18 @@ int hashList(Iterable<Object> arguments) {
   }
   return _Jenkins.finish(result);
 }
+
+/// Combine the [Object.hashCode] values of an arbitrary number of key and value
+/// objects from a [Map] into one value. This function will return the same
+/// value if given null as if given an empty map.
+int hashMap(Map<Object, Object> map) {
+  int result = 0;
+  if (map != null) {
+    final List<Object> keys = map.keys.toList()..sort();
+    for (Object key in keys) {
+      result = _Jenkins.combine(result, key);
+      result = _Jenkins.combine(result, map[key]);
+    }
+  }
+  return _Jenkins.finish(result);
+}