Fix Polymer licensing issues

third_party/web-animations-js/sources/web-animations-next.dev.js

-// Copyright 2014 Google Inc. All rights reserved.
-//
-// 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.
-var webAnimationsSourceTarget = 'web-animations-next';
-var WEB_ANIMATIONS_TESTING = false;
-(function() {
-  var scripts = document.getElementsByTagName('script');
-  var location = scripts[scripts.length - 1].src.replace(/[^\/]+$/, '');
-  document.write('<script src="' + location + 'target-config.js"></script>');
-  document.write('<script src="' + location + 'target-loader.js"></script>');
-})();