text: /**
   * Copyright 2020 The AMP HTML Authors. 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.
   */
  
  /**
   * Forces the return value from Set.prototype.add to always be the set
   * instance. IE11 returns undefined.
   *
   * @param {!Window} win
   */
  export function install(win) {
    const {Set} = win;
    const s = new Set();
    if (s.add(0) !== s) {
      const {add} = s;
  
      win.Object.defineProperty(Set.prototype, 'add', {
        enumerable: false,
        configurable: true,
        writable: true,
        value: function () {
          add.apply(this, arguments);
          return this;
        },
      });
    }
  }
  