/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 *
 * This file is a port of shadowCSS from webcomponents.js to TypeScript.
 * https://github.com/webcomponents/webcomponentsjs/blob/4efecd7e0e/src/ShadowCSS/ShadowCSS.js
 * https://github.com/angular/angular/blob/master/packages/compiler/src/shadow_css.ts
 */