angular-cn/modules/@angular/platform-browser/src/dom/dom_tokens.ts

import {OpaqueToken} from '@angular/core';

/**
 * A DI Token representing the main rendering context. In a browser this is the DOM Document.
 *
 * Note: Document might not be available in the Application Context when Application and Rendering
 * Contexts are not the same (e.g. when running the application into a Web Worker).
 */
export const DOCUMENT: OpaqueToken = new OpaqueToken('DocumentToken');