Fix Polymer licensing issues

third_party/web-animations-js/sources/src/visibility-handler.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.
-
-(function(scope, testing) {
-
-  function merge(left, right) {
-    if (left != 'visible' && right != 'visible') return;
-    return [0, 1, function(x) {
-      if (x <= 0) return left;
-      if (x >= 1) return right;
-      return 'visible';
-    }];
-  }
-
-  scope.addPropertiesHandler(String, merge, ['visibility']);
-
-})(webAnimations1);
-