Add userAgent support for screenshot

Author: Kikobeats

README.md

@@ -61,19 +61,25 @@ It takes an screenshot of the URL.
 
 `opts` provided are passed to [page.screenshot](https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#pagescreenshotoptions).
 
+It returns an [tmpStream](https://github.com/Kikobeats/create-temp-file2#create-temp-file2), with `path` where the temporal file live and `cleanup`/`cleanupSync` methods for clean the temporal file.
+
+If you want to customize where tmpStream live, pass [opts.tmpOptions](https://github.com/Kikobeats/create-temp-file2#createtempfileoptions).
+
 Additionally, you can setup:
 
 #### device
 
 Providing a valid [deviceDescriptor](https://github.com/GoogleChrome/puppeteer/blob/master/DeviceDescriptors.js) object.
 
-#### viewport
+#### userAgent
 
-Providing a valid [page.setViewport](https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#pagesetviewportviewport) object.
+It will setup an user Agent using 
 
-It returns an [tmpStream](https://github.com/Kikobeats/create-temp-file2#create-temp-file2), with `path` where the temporal file live and `cleanup`/`cleanupSync` methods for clean the temporal file.
+Providing a valid [page.setUserAgent](https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#pagesetuseragentuseragent) method.
 
-If you want to customize where tmpStream live, pass [opts.tmpOptions](https://github.com/Kikobeats/create-temp-file2#createtempfileoptions).
+#### viewport
+
+Providing a valid [page.setViewport](https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#pagesetviewportviewport) object.
 
 ### .text(url, [options], [cb])
 

index.js

@@ -1,6 +1,7 @@
 'use strict'
 
 const createTempFile = require('create-temp-file2')
+const isEmpty = require('lodash.isempty')
 const puppeteer = require('puppeteer')
 
 const { devices, getDevice } = require('./devices')
@@ -47,8 +48,11 @@ module.exports = launchOpts => {
       deviceName
     )
 
-    await page.setUserAgent(userAgent || deviceUserAgent)
-    await page.setViewport(Object.assign({}, deviceViewport, viewport))
+    const pageUserAgent = isEmpty(userAgent) ? deviceUserAgent : userAgent
+    await page.setUserAgent(pageUserAgent)
+
+    const pageViewport = Object.assign({}, deviceViewport, viewport)
+    await page.setViewport(pageViewport)
 
     await page.goto(url)
     await page.screenshot(Object.assign({ path, type }, opts))

package.json

@@ -30,6 +30,7 @@
   ],
   "dependencies": {
     "create-temp-file2": "~2.0.0",
+    "lodash.isempty": "~4.4.0",
     "puppeteer": "~0.12.0"
   },
   "devDependencies": {