feat: add option to specify the default viewport (#3005)

Fixes #1183.

lib/EmulationManager.js

@@ -25,7 +25,7 @@ class EmulationManager {
   }
 
   /**
-   * @param {!EmulationManager.Viewport} viewport
+   * @param {!Puppeteer.Viewport} viewport
    * @return {Promise<boolean>}
    */
   async emulateViewport(viewport) {
@@ -51,14 +51,4 @@ class EmulationManager {
   }
 }
 
-/**
- * @typedef {Object} EmulationManager.Viewport
- * @property {number} width
- * @property {number} height
- * @property {number=} deviceScaleFactor
- * @property {boolean=} isMobile
- * @property {boolean=} isLandscape
- * @property {boolean=} hasTouch
- */
-
 module.exports = EmulationManager;