update elements and fix some bugs

test/firebase_test_helpers.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+library iron_elements.test.firebase_test_helpers;
+
+import 'dart:js';
+import 'dart:math';
+import 'common.dart';
+import 'package:polymer_elements/firebase_collection.dart';
+
+var _rand = new Random();
+
+String firebaseTestProject = 'fb-element-demo';
+
+randomKey() {
+  return (0 | (_rand.nextDouble() * 999999999)).toString();
+}
+
+randomInt([min = 0, max = 10000]) {
+  return _rand.nextInt(max - min) + min;
+}
+
+randomObject([min = 0, max = 10000]) {
+  return {'value': randomInt(min, max)};
+}
+
+firebaseUrl(project, [path]) {
+  return 'https://$project.firebaseio.com${path != null ? '/$path'  : ''}';
+}
+
+fixtureLocation([data = const {}]) {
+  var firebase =
+      new JsObject(context['Firebase'], [firebaseUrl(firebaseTestProject)]);
+  return firebaseUrl(firebaseTestProject,
+      firebase.callMethod('push', [new JsObject.jsify(data)]).callMethod('key'));
+}
+
+removeLocation(location) {
+  new JsObject(context['Firebase'], [location]).callMethod('remove');
+}
+
+fixtureFirebase(fixtureName, [data = const {}]) {
+  FirebaseCollection firebase = fixture(fixtureName);
+  firebase.location = fixtureLocation(data);
+  return firebase;
+}
+
+removeFirebase(firebase) {
+  removeLocation(firebase.location);
+  firebase.disconnect();
+}
+
+arrayOfPrimitives(length) {
+  var array = [];
+
+  for (var i = 0; i < length; ++i) {
+    array.add(randomInt());
+  }
+
+  return array;
+}
+
+arrayOfObjects(length) {
+  var array = [];
+
+  for (var i = 0; i < length; ++i) {
+    array.add(randomObject());
+  }
+
+  return array;
+}