From 86397f66e06f1b122354ad3fe1002a8779803459 Mon Sep 17 00:00:00 2001
From: Andrey Lushnikov <lushnikov@chromium.org>
Date: Tue, 2 Jul 2019 00:39:55 +0200
Subject: [PATCH 1/7] chore: drop Node6 support

Node6 was end-of-life'ed in the end of April, 2019, with AWS Lambda
prohibiting updaets to the node6 runtime since June 30, 2019.

This makes it quite safe for us to remove the Node 6 support from the
repository.

From now on, all the subsequent commits will require Node 8.9.0+.
---
 .appveyor.yml                                 |   3 -
 .ci/node6/Dockerfile.linux                    |  17 --
 .cirrus.yml                                   |   9 -
 .travis.yml                                   |   3 -
 DeviceDescriptors.js                          |  13 +-
 Errors.js                                     |  13 +-
 README.md                                     |   3 +-
 .../puppeteer-firefox/DeviceDescriptors.js    |  13 +-
 .../puppeteer-firefox/lib/BrowserFetcher.js   |   8 +-
 experimental/puppeteer-firefox/lib/helper.js  |  16 --
 .../misc/install-preferences.js               |   4 +-
 index.js                                      |  23 +--
 install.js                                    |  18 --
 lib/BrowserFetcher.js                         |  12 +-
 lib/DOMWorld.js                               |   3 +-
 lib/Launcher.js                               |   5 +-
 lib/Page.js                                   |   4 +-
 lib/helper.js                                 |  25 +--
 package.json                                  |   8 +-
 test/evaluation.spec.js                       |  15 +-
 test/headful.spec.js                          |   7 +-
 test/launcher.spec.js                         |  11 +-
 utils/doclint/Source.js                       |  30 +---
 .../TransformAsyncFunctions.js                | 156 ------------------
 utils/node6-transform/index.js                |  63 -------
 utils/node6-transform/test/test.js            |  97 -----------
 26 files changed, 56 insertions(+), 523 deletions(-)
 delete mode 100644 .ci/node6/Dockerfile.linux
 delete mode 100644 utils/node6-transform/TransformAsyncFunctions.js
 delete mode 100644 utils/node6-transform/index.js
 delete mode 100644 utils/node6-transform/test/test.js

diff --git a/.appveyor.yml b/.appveyor.yml
index 2a8d3bef9a61f..3b835f32f6070 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -1,6 +1,5 @@
 environment:
   matrix:
-    - nodejs_version: "6.12.3"
     - nodejs_version: "8.11.3"
 
 build: off
@@ -13,6 +12,4 @@ install:
       npm run coverage  &&
       npm run test-doclint &&
       npm run test-types
-    ) else (
-      npm run unit-node6
     )
diff --git a/.ci/node6/Dockerfile.linux b/.ci/node6/Dockerfile.linux
deleted file mode 100644
index 77b416735d9db..0000000000000
--- a/.ci/node6/Dockerfile.linux
+++ /dev/null
@@ -1,17 +0,0 @@
-FROM node:6.12.3
-
-RUN apt-get update && \
-    apt-get -y install xvfb gconf-service libasound2 libatk1.0-0 libc6 libcairo2 libcups2 \
-      libdbus-1-3 libexpat1 libfontconfig1 libgcc1 libgconf-2-4 libgdk-pixbuf2.0-0 libglib2.0-0 \
-      libgtk-3-0 libnspr4 libpango-1.0-0 libpangocairo-1.0-0 libstdc++6 libx11-6 libx11-xcb1 libxcb1 \
-      libxcomposite1 libxcursor1 libxdamage1 libxext6 libxfixes3 libxi6 libxrandr2 libxrender1 libxss1 \
-      libxtst6 ca-certificates fonts-liberation libappindicator1 libnss3 lsb-release xdg-utils wget && \
-    rm -rf /var/lib/apt/lists/*
-
-# Add user so we don't need --no-sandbox.
-RUN groupadd -r pptruser && useradd -r -g pptruser -G audio,video pptruser \
-    && mkdir -p /home/pptruser/Downloads \
-    && chown -R pptruser:pptruser /home/pptruser
-
-# Run everything after as non-privileged user.
-USER pptruser
diff --git a/.cirrus.yml b/.cirrus.yml
index aaba646fd01e8..d73bed88f71d1 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -1,15 +1,6 @@
 env:
   DISPLAY: :99.0
 
-task:
-  matrix:
-    - name: Chromium (node6 + linux)
-      container:
-        dockerfile: .ci/node6/Dockerfile.linux
-      xvfb_start_background_script: Xvfb :99 -ac -screen 0 1024x768x24
-  install_script: npm install --unsafe-perm
-  test_script: npm run unit-node6
-
 task:
   matrix:
     - name: Chromium (node8 + linux)
diff --git a/.travis.yml b/.travis.yml
index 24641f8dcab8d..5a470e9ee0490 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,13 +24,10 @@ script:
   - 'if [ "$NODE8" = "true" ]; then npm run test-types; fi'
   - 'if [ "$NODE8" = "true" ]; then npm run bundle; fi'
   - 'if [ "$NODE8" = "true" ]; then npm run unit-bundle; fi'
-  - 'if [ "$NODE6" = "true" ]; then npm run unit-node6; fi'
 jobs:
   include:
     - node_js: "8.11.3"
       env: NODE8=true
-    - node_js: "6.12.3"
-      env: NODE6=true
 before_deploy: "npm run apply-next-version"
 deploy:
   provider: npm
diff --git a/DeviceDescriptors.js b/DeviceDescriptors.js
index a89a09829000d..05135a115368c 100644
--- a/DeviceDescriptors.js
+++ b/DeviceDescriptors.js
@@ -14,15 +14,4 @@
  * limitations under the License.
  */
 
-let asyncawait = true;
-try {
-  new Function('async function test(){await 1}');
-} catch (error) {
-  asyncawait = false;
-}
-
-// If node does not support async await, use the compiled version.
-if (asyncawait)
-  module.exports = require('./lib/DeviceDescriptors');
-else
-  module.exports = require('./node6/lib/DeviceDescriptors');
+module.exports = require('./lib/DeviceDescriptors');
diff --git a/Errors.js b/Errors.js
index dc41298ac12b2..4779e1d850812 100644
--- a/Errors.js
+++ b/Errors.js
@@ -14,15 +14,4 @@
  * limitations under the License.
  */
 
-let asyncawait = true;
-try {
-  new Function('async function test(){await 1}');
-} catch (error) {
-  asyncawait = false;
-}
-
-// If node does not support async await, use the compiled version.
-if (asyncawait)
-  module.exports = require('./lib/Errors');
-else
-  module.exports = require('./node6/lib/Errors');
+module.exports = require('./lib/Errors');
diff --git a/README.md b/README.md
index 2b66be927686f..a84f02af4083c 100644
--- a/README.md
+++ b/README.md
@@ -57,7 +57,8 @@ See [puppeteer vs puppeteer-core](https://github.com/GoogleChrome/puppeteer/blob
 
 ### Usage
 
-Note: Puppeteer requires at least Node v6.4.0, but the examples below use async/await which is only supported in Node v7.6.0 or greater.
+Note: Prior to v1.18.1, Puppeteer required at least Node v6.4.0. All subsequent versions rely on
+Node 8.9.0+. All examples below use async/await which is only supported in Node v7.6.0 or greater.
 
 Puppeteer will be familiar to people using other browser testing frameworks. You create an instance
 of `Browser`, open pages, and then manipulate them with [Puppeteer's API](https://github.com/GoogleChrome/puppeteer/blob/v1.18.1/docs/api.md#).
diff --git a/experimental/puppeteer-firefox/DeviceDescriptors.js b/experimental/puppeteer-firefox/DeviceDescriptors.js
index a89a09829000d..05135a115368c 100644
--- a/experimental/puppeteer-firefox/DeviceDescriptors.js
+++ b/experimental/puppeteer-firefox/DeviceDescriptors.js
@@ -14,15 +14,4 @@
  * limitations under the License.
  */
 
-let asyncawait = true;
-try {
-  new Function('async function test(){await 1}');
-} catch (error) {
-  asyncawait = false;
-}
-
-// If node does not support async await, use the compiled version.
-if (asyncawait)
-  module.exports = require('./lib/DeviceDescriptors');
-else
-  module.exports = require('./node6/lib/DeviceDescriptors');
+module.exports = require('./lib/DeviceDescriptors');
diff --git a/experimental/puppeteer-firefox/lib/BrowserFetcher.js b/experimental/puppeteer-firefox/lib/BrowserFetcher.js
index c7d1250e4c1ee..c222754d32584 100644
--- a/experimental/puppeteer-firefox/lib/BrowserFetcher.js
+++ b/experimental/puppeteer-firefox/lib/BrowserFetcher.js
@@ -82,10 +82,10 @@ function downloadURL(product, platform, host, revision) {
   return util.format(downloadURLs[product][platform], host, revision, archiveName(product, platform, revision));
 }
 
-const readdirAsync = helper.promisify(fs.readdir.bind(fs));
-const mkdirAsync = helper.promisify(fs.mkdir.bind(fs));
-const unlinkAsync = helper.promisify(fs.unlink.bind(fs));
-const chmodAsync = helper.promisify(fs.chmod.bind(fs));
+const readdirAsync = util.promisify(fs.readdir.bind(fs));
+const mkdirAsync = util.promisify(fs.mkdir.bind(fs));
+const unlinkAsync = util.promisify(fs.unlink.bind(fs));
+const chmodAsync = util.promisify(fs.chmod.bind(fs));
 
 function existsAsync(filePath) {
   let fulfill = null;
diff --git a/experimental/puppeteer-firefox/lib/helper.js b/experimental/puppeteer-firefox/lib/helper.js
index 78dd01d6889e0..cd4d0e9f4c222 100644
--- a/experimental/puppeteer-firefox/lib/helper.js
+++ b/experimental/puppeteer-firefox/lib/helper.js
@@ -65,22 +65,6 @@ class Helper {
     }
   }
 
-  static promisify(nodeFunction) {
-    function promisified(...args) {
-      return new Promise((resolve, reject) => {
-        function callback(err, ...result) {
-          if (err)
-            return reject(err);
-          if (result.length === 1)
-            return resolve(result[0]);
-          return resolve(result);
-        }
-        nodeFunction.call(null, ...args, callback);
-      });
-    }
-    return promisified;
-  }
-
   /**
    * @param {!Object} obj
    * @return {boolean}
diff --git a/experimental/puppeteer-firefox/misc/install-preferences.js b/experimental/puppeteer-firefox/misc/install-preferences.js
index c536baa7eab6f..b48267091ddd6 100644
--- a/experimental/puppeteer-firefox/misc/install-preferences.js
+++ b/experimental/puppeteer-firefox/misc/install-preferences.js
@@ -1,14 +1,14 @@
 const os = require('os');
 const fs = require('fs');
 const path = require('path');
+const util = require('util');
 
 // Install browser preferences after downloading and unpacking
 // firefox instances.
 // Based on:   https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Enterprise_deployment_before_60#Configuration
 async function installFirefoxPreferences(executablePath) {
   const firefoxFolder = path.dirname(executablePath);
-  const {helper} = require('../lib/helper');
-  const mkdirAsync = helper.promisify(fs.mkdir.bind(fs));
+  const mkdirAsync = util.promisify(fs.mkdir.bind(fs));
 
   let prefPath = '';
   let configPath = '';
diff --git a/index.js b/index.js
index e7143fb3a5b18..a73d4d23d5fc6 100644
--- a/index.js
+++ b/index.js
@@ -14,25 +14,16 @@
  * limitations under the License.
  */
 
-let asyncawait = true;
-try {
-  new Function('async function test(){await 1}');
-} catch (error) {
-  asyncawait = false;
-}
-
-if (asyncawait) {
-  const {helper} = require('./lib/helper');
-  const api = require('./lib/api');
-  for (const className in api) {
-    // Puppeteer-web excludes certain classes from bundle, e.g. BrowserFetcher.
-    if (typeof api[className] === 'function')
-      helper.installAsyncStackHooks(api[className]);
-  }
+const {helper} = require('./lib/helper');
+const api = require('./lib/api');
+for (const className in api) {
+  // Puppeteer-web excludes certain classes from bundle, e.g. BrowserFetcher.
+  if (typeof api[className] === 'function')
+    helper.installAsyncStackHooks(api[className]);
 }
 
 // If node does not support async await, use the compiled version.
-const Puppeteer = asyncawait ? require('./lib/Puppeteer') : require('./node6/lib/Puppeteer');
+const Puppeteer = require('./lib/Puppeteer');
 const packageJson = require('./package.json');
 const preferredRevision = packageJson.puppeteer.chromium_revision;
 const isPuppeteerCore = packageJson.name === 'puppeteer-core';
diff --git a/install.js b/install.js
index d0e6c9181506a..2e3f52b540411 100644
--- a/install.js
+++ b/install.js
@@ -18,8 +18,6 @@
 if (require('./package.json').name === 'puppeteer-core')
   return;
 
-buildNode6IfNecessary();
-
 if (process.env.PUPPETEER_SKIP_CHROMIUM_DOWNLOAD) {
   logPolitely('**INFO** Skipping Chromium download. "PUPPETEER_SKIP_CHROMIUM_DOWNLOAD" environment variable was found.');
   return;
@@ -109,22 +107,6 @@ function toMegabytes(bytes) {
   return `${Math.round(mb * 10) / 10} Mb`;
 }
 
-function buildNode6IfNecessary() {
-  const fs = require('fs');
-  const path = require('path');
-
-  // if this package is installed from NPM, then it already has up-to-date node6
-  // folder.
-  if (!fs.existsSync(path.join('utils', 'node6-transform')))
-    return;
-  // if async/await is supported, then node6 is not needed.
-  if (supportsAsyncAwait())
-    return;
-  // Re-build node6/ folder.
-  logPolitely('Building Puppeteer for Node 6');
-  require(path.join(__dirname, 'utils', 'node6-transform'));
-}
-
 function supportsAsyncAwait() {
   try {
     new Function('async function test(){await 1}');
diff --git a/lib/BrowserFetcher.js b/lib/BrowserFetcher.js
index 4f0492bdcecac..cea6e3ee97f13 100644
--- a/lib/BrowserFetcher.js
+++ b/lib/BrowserFetcher.js
@@ -17,10 +17,10 @@
 const os = require('os');
 const fs = require('fs');
 const path = require('path');
-const extract = require('extract-zip');
 const util = require('util');
+const extract = require('extract-zip');
 const URL = require('url');
-const {helper, assert} = require('./helper');
+const {assert} = require('./helper');
 const removeRecursive = require('rimraf');
 // @ts-ignore
 const ProxyAgent = require('https-proxy-agent');
@@ -64,10 +64,10 @@ function downloadURL(platform, host, revision) {
   return util.format(downloadURLs[platform], host, revision, archiveName(platform, revision));
 }
 
-const readdirAsync = helper.promisify(fs.readdir.bind(fs));
-const mkdirAsync = helper.promisify(fs.mkdir.bind(fs));
-const unlinkAsync = helper.promisify(fs.unlink.bind(fs));
-const chmodAsync = helper.promisify(fs.chmod.bind(fs));
+const readdirAsync = util.promisify(fs.readdir.bind(fs));
+const mkdirAsync = util.promisify(fs.mkdir.bind(fs));
+const unlinkAsync = util.promisify(fs.unlink.bind(fs));
+const chmodAsync = util.promisify(fs.chmod.bind(fs));
 
 function existsAsync(filePath) {
   let fulfill = null;
diff --git a/lib/DOMWorld.js b/lib/DOMWorld.js
index 1668fad003483..6894f82151eca 100644
--- a/lib/DOMWorld.js
+++ b/lib/DOMWorld.js
@@ -15,10 +15,11 @@
  */
 
 const fs = require('fs');
+const util = require('util');
 const {helper, assert} = require('./helper');
 const {LifecycleWatcher} = require('./LifecycleWatcher');
 const {TimeoutError} = require('./Errors');
-const readFileAsync = helper.promisify(fs.readFile);
+const readFileAsync = util.promisify(fs.readFile);
 
 /**
  * @unrestricted
diff --git a/lib/Launcher.js b/lib/Launcher.js
index 8a92ab7486e1f..4fd5e52fdd8d0 100644
--- a/lib/Launcher.js
+++ b/lib/Launcher.js
@@ -15,6 +15,7 @@
  */
 const os = require('os');
 const path = require('path');
+const util = require('util');
 const http = require('http');
 const https = require('https');
 const URL = require('url');
@@ -30,8 +31,8 @@ const {TimeoutError} = require('./Errors');
 const WebSocketTransport = require('./WebSocketTransport');
 const PipeTransport = require('./PipeTransport');
 
-const mkdtempAsync = helper.promisify(fs.mkdtemp);
-const removeFolderAsync = helper.promisify(removeFolder);
+const mkdtempAsync = util.promisify(fs.mkdtemp);
+const removeFolderAsync = util.promisify(removeFolder);
 
 const CHROME_PROFILE_PATH = path.join(os.tmpdir(), 'puppeteer_dev_profile-');
 
diff --git a/lib/Page.js b/lib/Page.js
index 80d960dc3b043..e38524dee8f99 100644
--- a/lib/Page.js
+++ b/lib/Page.js
@@ -17,6 +17,7 @@
 const fs = require('fs');
 const EventEmitter = require('events');
 const mime = require('mime');
+const util = require('util');
 const {Events} = require('./Events');
 const {Connection} = require('./Connection');
 const {Dialog} = require('./Dialog');
@@ -30,7 +31,8 @@ const {Worker} = require('./Worker');
 const {createJSHandle} = require('./JSHandle');
 const {Accessibility} = require('./Accessibility');
 const {TimeoutSettings} = require('./TimeoutSettings');
-const writeFileAsync = helper.promisify(fs.writeFile);
+
+const writeFileAsync = util.promisify(fs.writeFile);
 
 class Page extends EventEmitter {
   /**
diff --git a/lib/helper.js b/lib/helper.js
index e12d63dbeceed..ca53f0080a2f4 100644
--- a/lib/helper.js
+++ b/lib/helper.js
@@ -16,6 +16,11 @@
 const {TimeoutError} = require('./Errors');
 const debugError = require('debug')(`puppeteer:error`);
 const fs = require('fs');
+const util = require('util');
+
+const openAsync = util.promisify(fs.open);
+const writeAsync = util.promisify(fs.write);
+const closeAsync = util.promisify(fs.close);
 
 class Helper {
   /**
@@ -156,22 +161,6 @@ class Helper {
     return typeof obj === 'number' || obj instanceof Number;
   }
 
-  static promisify(nodeFunction) {
-    function promisified(...args) {
-      return new Promise((resolve, reject) => {
-        function callback(err, ...result) {
-          if (err)
-            return reject(err);
-          if (result.length === 1)
-            return resolve(result[0]);
-          return resolve(result);
-        }
-        nodeFunction.call(null, ...args, callback);
-      });
-    }
-    return promisified;
-  }
-
   /**
    * @param {!NodeJS.EventEmitter} emitter
    * @param {(string|symbol)} eventName
@@ -254,10 +243,6 @@ class Helper {
   }
 }
 
-const openAsync = Helper.promisify(fs.open);
-const writeAsync = Helper.promisify(fs.write);
-const closeAsync = Helper.promisify(fs.close);
-
 /**
  * @param {*} value
  * @param {string=} message
diff --git a/package.json b/package.json
index aa64a5607b228..03585a4372e2f 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "main": "index.js",
   "repository": "github:GoogleChrome/puppeteer",
   "engines": {
-    "node": ">=6.4.0"
+    "node": ">=8.9.0"
   },
   "puppeteer": {
     "chromium_revision": "673587"
@@ -15,14 +15,11 @@
     "funit": "BROWSER=firefox node test/test.js",
     "debug-unit": "node --inspect-brk test/test.js",
     "test-doclint": "node utils/doclint/check_public_api/test/test.js && node utils/doclint/preprocessor/test.js",
-    "test": "npm run lint --silent && npm run coverage && npm run test-doclint && npm run test-node6-transformer && npm run test-types",
+    "test": "npm run lint --silent && npm run coverage && npm run test-doclint && npm run test-types",
     "install": "node install.js",
     "lint": "([ \"$CI\" = true ] && eslint --quiet -f codeframe . || eslint .) && npm run tsc && npm run doc",
     "doc": "node utils/doclint/cli.js",
     "coverage": "cross-env COVERAGE=true npm run unit",
-    "test-node6-transformer": "node utils/node6-transform/test/test.js",
-    "build": "node utils/node6-transform/index.js && node utils/doclint/generate_types",
-    "unit-node6": "node node6/test/test.js",
     "tsc": "tsc -p .",
     "prepublishOnly": "npm run build",
     "apply-next-version": "node utils/apply_next_version.js",
@@ -63,7 +60,6 @@
   },
   "browser": {
     "./lib/BrowserFetcher.js": false,
-    "./node6/lib/Puppeteer": false,
     "ws": "./utils/browser/WebSocket",
     "fs": false,
     "child_process": false,
diff --git a/test/evaluation.spec.js b/test/evaluation.spec.js
index ee3988dcc0b2d..b91ff03d7490e 100644
--- a/test/evaluation.spec.js
+++ b/test/evaluation.spec.js
@@ -16,13 +16,6 @@
 
 const utils = require('./utils');
 
-let asyncawait = true;
-try {
-  new Function('async function foo() {await 1}');
-} catch (e) {
-  asyncawait = false;
-}
-
 const bigint = typeof BigInt !== 'undefined';
 
 module.exports.addTests = function({testRunner, expect}) {
@@ -74,14 +67,12 @@ module.exports.addTests = function({testRunner, expect}) {
     it_fails_ffox('should return undefined for objects with symbols', async({page, server}) => {
       expect(await page.evaluate(() => [Symbol('foo4')])).toBe(undefined);
     });
-    (asyncawait ? it : xit)('should work with function shorthands', async({page, server}) => {
-      // trick node6 transpiler to not touch our object.
-      // TODO(lushnikov): remove eval once Node6 is dropped.
-      const a = eval(`({
+    it('should work with function shorthands', async({page, server}) => {
+      const a = {
         sum(a, b) { return a + b; },
 
         async mult(a, b) { return a * b; }
-      })`);
+      };
       expect(await page.evaluate(a.sum, 1, 2)).toBe(3);
       expect(await page.evaluate(a.mult, 2, 4)).toBe(8);
     });
diff --git a/test/headful.spec.js b/test/headful.spec.js
index 965fc2431f423..3128c1657ff08 100644
--- a/test/headful.spec.js
+++ b/test/headful.spec.js
@@ -17,11 +17,12 @@
 const path = require('path');
 const os = require('os');
 const fs = require('fs');
-const {helper} = require('../lib/helper');
-const rmAsync = helper.promisify(require('rimraf'));
+const util = require('util');
 const utils = require('./utils');
 const {waitEvent} = utils;
-const mkdtempAsync = helper.promisify(fs.mkdtemp);
+
+const rmAsync = util.promisify(require('rimraf'));
+const mkdtempAsync = util.promisify(fs.mkdtemp);
 
 const TMP_FOLDER = path.join(os.tmpdir(), 'pptr_tmp_folder-');
 
diff --git a/test/launcher.spec.js b/test/launcher.spec.js
index 510d1c9ef1bb4..00243215375fe 100644
--- a/test/launcher.spec.js
+++ b/test/launcher.spec.js
@@ -16,11 +16,12 @@
 const fs = require('fs');
 const os = require('os');
 const path = require('path');
-const {helper} = require('../lib/helper');
-const rmAsync = helper.promisify(require('rimraf'));
-const mkdtempAsync = helper.promisify(fs.mkdtemp);
-const readFileAsync = helper.promisify(fs.readFile);
-const statAsync = helper.promisify(fs.stat);
+const util = require('util');
+
+const rmAsync = util.promisify(require('rimraf'));
+const mkdtempAsync = util.promisify(fs.mkdtemp);
+const readFileAsync = util.promisify(fs.readFile);
+const statAsync = util.promisify(fs.stat);
 const TMP_FOLDER = path.join(os.tmpdir(), 'pptr_tmp_folder-');
 const utils = require('./utils');
 
diff --git a/utils/doclint/Source.js b/utils/doclint/Source.js
index 455f41924372e..dd77eac9469d3 100644
--- a/utils/doclint/Source.js
+++ b/utils/doclint/Source.js
@@ -15,11 +15,12 @@
  */
 
 const path = require('path');
+const util = require('util');
 const fs = require('fs');
 
-const readFileAsync = promisify(fs.readFile);
-const readdirAsync = promisify(fs.readdir);
-const writeFileAsync = promisify(fs.writeFile);
+const readFileAsync = util.promisify(fs.readFile);
+const readdirAsync = util.promisify(fs.readdir);
+const writeFileAsync = util.promisify(fs.writeFile);
 
 const PROJECT_DIR = path.join(__dirname, '..', '..');
 
@@ -110,26 +111,3 @@ class Source {
 }
 module.exports = Source;
 
-/**
- * @param {function(?)} nodeFunction
- * @return {function(?):!Promise<?>}
- */
-function promisify(nodeFunction) {
-  /**
-   * @param {!Array<?>} options
-   * @return {!Promise<?>}
-   */
-  return function(...options) {
-    return new Promise(function(fulfill, reject) {
-      options.push(callback);
-      nodeFunction.call(null, ...options);
-      function callback(err, result) {
-        if (err)
-          reject(err);
-        else
-          fulfill(result);
-      }
-    });
-  };
-}
-
diff --git a/utils/node6-transform/TransformAsyncFunctions.js b/utils/node6-transform/TransformAsyncFunctions.js
deleted file mode 100644
index 5903d89839d11..0000000000000
--- a/utils/node6-transform/TransformAsyncFunctions.js
+++ /dev/null
@@ -1,156 +0,0 @@
-/**
- * Copyright 2017 Google Inc. 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.
- */
-
-const esprima = require('esprima');
-const ESTreeWalker = require('../ESTreeWalker');
-
-// This is converted from Babel's "transform-async-to-generator"
-// https://babeljs.io/docs/plugins/transform-async-to-generator/
-const asyncToGenerator = fn => {
-  const gen = fn.call(this);
-  return new Promise((resolve, reject) => {
-    function step(key, arg) {
-      let info, value;
-      try {
-        info = gen[key](arg);
-        value = info.value;
-      } catch (error) {
-        reject(error);
-        return;
-      }
-      if (info.done) {
-        resolve(value);
-      } else {
-        return Promise.resolve(value).then(
-            value => {
-              step('next', value);
-            },
-            err => {
-              step('throw', err);
-            });
-      }
-    }
-    return step('next');
-  });
-};
-
-/**
- * @param {string} text
- * @return {string}
- */
-function transformAsyncFunctions(text) {
-  /**
-   * @type {!Array<{from: number, to: number, replacement: string}>}
-   */
-  const edits = [];
-
-  const ast = esprima.parseScript(text, {range: true, tolerant: true});
-  const walker = new ESTreeWalker(node => {
-    if (node.type === 'FunctionExpression' || node.type === 'FunctionDeclaration' || node.type === 'ArrowFunctionExpression')
-      onBeforeFunction(node);
-    else if (node.type === 'AwaitExpression')
-      onBeforeAwait(node);
-  }, node => {
-    if (node.type === 'FunctionExpression' || node.type === 'FunctionDeclaration' || node.type === 'ArrowFunctionExpression')
-      onAfterFunction(node);
-    else if (node.type === 'AwaitExpression')
-      onAfterAwait(node);
-  });
-  walker.walk(ast);
-
-  edits.reverse();
-  for (const {replacement, from, to} of edits)
-    text = text.substring(0, from) + replacement + text.substring(to);
-
-  return text;
-
-  /**
-   * @param {ESTree.Node} node
-   */
-  function onBeforeFunction(node) {
-    if (!node.async) return;
-
-    let range;
-    if (node.parent.type === 'MethodDefinition')
-      range = node.parent.range;
-    else
-      range = node.range;
-    const index = text.substring(range[0], range[1]).indexOf('async') + range[0];
-    insertText(index, index + 'async'.length, '/* async */');
-
-    let before = `{return (${asyncToGenerator.toString()})(function*()`;
-    if (node.body.type !== 'BlockStatement') {
-      before += `{ return `;
-
-      // Remove parentheses that might wrap an arrow function
-      const beforeBody = text.substring(node.range[0], node.body.range[0]);
-      if (/\(\s*$/.test(beforeBody)) {
-        const openParen = node.range[0] + beforeBody.lastIndexOf('(');
-        insertText(openParen, openParen + 1, ' ');
-      }
-    }
-
-
-    insertText(node.body.range[0], node.body.range[0], before);
-  }
-
-  /**
-   * @param {ESTree.Node} node
-   */
-  function onAfterFunction(node) {
-    if (!node.async) return;
-
-    let after = `);}`;
-    if (node.body.type !== 'BlockStatement')
-      after = `; }` + after;
-    insertText(node.body.range[1], node.body.range[1], after);
-
-    if (node.body.type !== 'BlockStatement') {
-      // Remove parentheses that might wrap an arrow function
-      const beforeBody = text.substring(node.range[0], node.body.range[0]);
-      if (/\(\s*$/.test(beforeBody)) {
-        const afterBody = text.substring(node.body.range[1], node.range[1]);
-        const closeParen = node.body.range[1] + afterBody.indexOf(')');
-        insertText(closeParen, closeParen + 1, ' ');
-      }
-    }
-  }
-
-  /**
-   * @param {ESTree.Node} node
-   */
-  function onBeforeAwait(node) {
-    const index = text.substring(node.range[0], node.range[1]).indexOf('await') + node.range[0];
-    insertText(index, index + 'await'.length, '(yield');
-  }
-
-  /**
-   * @param {ESTree.Node} node
-   */
-  function onAfterAwait(node) {
-    insertText(node.range[1], node.range[1], ')');
-  }
-
-  /**
-   * @param {number} from
-   * @param {number} to
-   */
-  function insertText(from, to, replacement) {
-    edits.push({from, to, replacement});
-  }
-}
-
-module.exports = transformAsyncFunctions;
\ No newline at end of file
diff --git a/utils/node6-transform/index.js b/utils/node6-transform/index.js
deleted file mode 100644
index 967899f9a104d..0000000000000
--- a/utils/node6-transform/index.js
+++ /dev/null
@@ -1,63 +0,0 @@
-/**
- * Copyright 2017 Google Inc. 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.
- */
-
-const fs = require('fs');
-const path = require('path');
-const removeRecursive = require('rimraf').sync;
-const transformAsyncFunctions = require('./TransformAsyncFunctions');
-
-const root = path.join(__dirname, '..', '..');
-const dest = path.join(__dirname, '..', '..', 'node6');
-
-const excludes = [
-  path.resolve(root, 'test', 'assets'),
-];
-
-if (fs.existsSync(dest))
-  removeRecursive(dest);
-fs.mkdirSync(dest);
-fs.mkdirSync(path.join(dest, 'utils'));
-
-copyFolder(path.join(root, 'lib'), path.join(dest, 'lib'));
-copyFolder(path.join(root, 'test'), path.join(dest, 'test'));
-copyFolder(path.join(root, 'utils', 'testrunner'), path.join(dest, 'utils', 'testrunner'));
-copyFolder(path.join(root, 'utils', 'testserver'), path.join(dest, 'utils', 'testserver'));
-
-function copyFolder(source, target) {
-  if (fs.existsSync(target))
-    removeRecursive(target);
-  fs.mkdirSync(target);
-
-  fs.readdirSync(source).forEach(file => {
-    const from = path.join(source, file);
-    const to = path.join(target, file);
-    if (fs.lstatSync(from).isDirectory())
-      copyFolder(from, to);
-    else
-      copyFile(from, to);
-  });
-}
-
-function copyFile(from, to) {
-  let text = fs.readFileSync(from);
-  const isExcluded = excludes.some(exclude => from.startsWith(exclude));
-  if (!isExcluded && from.endsWith('.js')) {
-    text = text.toString();
-    const prefix = text.startsWith('#!') ? text.substring(0, text.indexOf('\n')) : '';
-    text = prefix + transformAsyncFunctions(text.substring(prefix.length));
-  }
-  fs.writeFileSync(to, text);
-}
diff --git a/utils/node6-transform/test/test.js b/utils/node6-transform/test/test.js
deleted file mode 100644
index 46836d848ec8a..0000000000000
--- a/utils/node6-transform/test/test.js
+++ /dev/null
@@ -1,97 +0,0 @@
-/**
- * Copyright 2017 Google Inc. 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.
- */
-const transformAsyncFunctions = require('../TransformAsyncFunctions');
-
-const {TestRunner, Reporter, Matchers}  = require('../../testrunner/');
-const runner = new TestRunner();
-new Reporter(runner);
-
-const {describe, xdescribe, fdescribe} = runner;
-const {it, fit, xit} = runner;
-const {beforeAll, beforeEach, afterAll, afterEach} = runner;
-
-const {expect} = new Matchers();
-
-describe('TransformAsyncFunctions', function() {
-  it('should convert a function expression', function(done) {
-    const input = `(async function(){ return 123 })()`;
-    const output = eval(transformAsyncFunctions(input));
-    expect(output instanceof Promise).toBe(true);
-    output.then(result => expect(result).toBe(123)).then(done);
-  });
-  it('should convert an arrow function', function(done) {
-    const input = `(async () => 123)()`;
-    const output = eval(transformAsyncFunctions(input));
-    expect(output instanceof Promise).toBe(true);
-    output.then(result => expect(result).toBe(123)).then(done);
-  });
-  it('should convert an arrow function with curly braces', function(done) {
-    const input = `(async () => { return 123 })()`;
-    const output = eval(transformAsyncFunctions(input));
-    expect(output instanceof Promise).toBe(true);
-    output.then(result => expect(result).toBe(123)).then(done);
-  });
-  it('should convert a function declaration', function(done) {
-    const input = `async function f(){ return 123; } f();`;
-    const output = eval(transformAsyncFunctions(input));
-    expect(output instanceof Promise).toBe(true);
-    output.then(result => expect(result).toBe(123)).then(done);
-  });
-  it('should convert await', function(done) {
-    const input = `async function f(){ return 23 + await Promise.resolve(100); } f();`;
-    const output = eval(transformAsyncFunctions(input));
-    expect(output instanceof Promise).toBe(true);
-    output.then(result => expect(result).toBe(123)).then(done);
-  });
-  it('should convert method', function(done) {
-    const input = `class X{async f() { return 123 }} (new X()).f();`;
-    const output = eval(transformAsyncFunctions(input));
-    expect(output instanceof Promise).toBe(true);
-    output.then(result => expect(result).toBe(123)).then(done);
-  });
-  it('should pass arguments', function(done) {
-    const input = `(async function(a, b){ return await a + await b })(Promise.resolve(100), 23)`;
-    const output = eval(transformAsyncFunctions(input));
-    expect(output instanceof Promise).toBe(true);
-    output.then(result => expect(result).toBe(123)).then(done);
-  });
-  it('should still work across eval', function(done) {
-    const input = `var str = (async function(){ return 123; }).toString(); eval('(' + str + ')')();`;
-    const output = eval(transformAsyncFunctions(input));
-    expect(output instanceof Promise).toBe(true);
-    output.then(result => expect(result).toBe(123)).then(done);
-  });
-  it('should work with double await', function(done) {
-    const input = `async function f(){ return 23 + await Promise.resolve(50 + await Promise.resolve(50)); } f();`;
-    const output = eval(transformAsyncFunctions(input));
-    expect(output instanceof Promise).toBe(true);
-    output.then(result => expect(result).toBe(123)).then(done);
-  });
-  it('should work paren around arrow function', function(done) {
-    const input = `(async x => ( 123))()`;
-    const output = eval(transformAsyncFunctions(input));
-    expect(output instanceof Promise).toBe(true);
-    output.then(result => expect(result).toBe(123)).then(done);
-  });
-  it('should work async arrow with await', function(done) {
-    const input = `(async() => await 123)()`;
-    const output = eval(transformAsyncFunctions(input));
-    expect(output instanceof Promise).toBe(true);
-    output.then(result => expect(result).toBe(123)).then(done);
-  });
-});
-
-runner.run();

From 9cea37974375043154524f87e2630d30a639554e Mon Sep 17 00:00:00 2001
From: Mathias Bynens <mathias@qiwi.be>
Date: Wed, 11 Sep 2019 10:20:28 +0200
Subject: [PATCH 2/7] Remove supportsAsyncAwait

---
 install.js | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/install.js b/install.js
index 2e3f52b540411..1e9faf53ad0e2 100644
--- a/install.js
+++ b/install.js
@@ -107,18 +107,7 @@ function toMegabytes(bytes) {
   return `${Math.round(mb * 10) / 10} Mb`;
 }
 
-function supportsAsyncAwait() {
-  try {
-    new Function('async function test(){await 1}');
-  } catch (error) {
-    return false;
-  }
-  return true;
-}
-
 function generateProtocolTypesIfNecessary(updated) {
-  if (!supportsAsyncAwait())
-    return;
   const fs = require('fs');
   const path = require('path');
   if (!fs.existsSync(path.join(__dirname, 'utils', 'protocol-types-generator')))

From 85a3386fdf2fa6a73a652705cc7a3377e0e27b30 Mon Sep 17 00:00:00 2001
From: Mathias Bynens <mathias@qiwi.be>
Date: Wed, 16 Oct 2019 10:31:24 +0200
Subject: [PATCH 3/7] Add LTS note to README

---
 README.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/README.md b/README.md
index ae705d9366eb8..468eed34f5373 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,8 @@ See [puppeteer vs puppeteer-core](https://github.com/GoogleChrome/puppeteer/blob
 
 ### Usage
 
+Puppeteer follows the latest [maintenance LTS](https://github.com/nodejs/Release#release-schedule) version of Node.
+
 Note: Prior to v1.18.1, Puppeteer required at least Node v6.4.0. All subsequent versions rely on
 Node 8.9.0+. All examples below use async/await which is only supported in Node v7.6.0 or greater.
 

From b10db48534c545c5afb31b65b35a74e3b1eaa856 Mon Sep 17 00:00:00 2001
From: Mathias Bynens <mathias@qiwi.be>
Date: Wed, 16 Oct 2019 10:50:40 +0200
Subject: [PATCH 4/7] Bump to latest Node.js v8 LTS

---
 .appveyor.yml | 2 +-
 .travis.yml   | 4 ++--
 package.json  | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/.appveyor.yml b/.appveyor.yml
index 49f62d4f1b673..6a2eeff1eb13b 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -1,6 +1,6 @@
 environment:
   matrix:
-    - nodejs_version: "8.11.3"
+    - nodejs_version: "8.16.2"
       FLAKINESS_DASHBOARD_NAME: Appveyor Chromium (Win + node8)
   FLAKINESS_DASHBOARD_PASSWORD:
     secure: g66jP+j6C+hkXLutBV9fdxB5fRJgcQQzy93SgQzXUmcCl/RjkJwnzyHvX0xfCVnv
diff --git a/.travis.yml b/.travis.yml
index 3168bdd3be179..86cb12a91e7ec 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -26,12 +26,12 @@ script:
   - 'if [ "$NODE8" = "true" ]; then npm run unit-bundle; fi'
 jobs:
   include:
-    - node_js: "8.11.3"
+    - node_js: "8.16.2"
       env:
         - NODE8=true
         - FLAKINESS_DASHBOARD_NAME="Travis Chromium (node8 + linux)"
         - FLAKINESS_DASHBOARD_BUILD_URL="${TRAVIS_JOB_WEB_URL}"
-    - node_js: "8.11.3"
+    - node_js: "8.16.2"
       env:
         - FIREFOX=true
         - FLAKINESS_DASHBOARD_NAME="Travis Firefox (node8 + linux)"
diff --git a/package.json b/package.json
index 13ace7c1debf7..618e998facec9 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "main": "index.js",
   "repository": "github:GoogleChrome/puppeteer",
   "engines": {
-    "node": ">=8.9.0"
+    "node": ">=8.16.2"
   },
   "puppeteer": {
     "chromium_revision": "686378"

From e13199474a86320cfb4f7271a486a89dcd650f81 Mon Sep 17 00:00:00 2001
From: Mathias Bynens <mathias@qiwi.be>
Date: Wed, 16 Oct 2019 13:07:24 +0200
Subject: [PATCH 5/7] Tweak flaky test

This shouldn't affect its flakiness.
---
 test/launcher.spec.js | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/test/launcher.spec.js b/test/launcher.spec.js
index bb415ffa1220d..78fdd93cef1d0 100644
--- a/test/launcher.spec.js
+++ b/test/launcher.spec.js
@@ -234,9 +234,10 @@ module.exports.addTests = function({testRunner, expect, defaultBrowserOptions, p
         const browser = await puppeteer.launch(options);
         const pages = await browser.pages();
         expect(pages.length).toBe(1);
-        if (pages[0].url() !== server.EMPTY_PAGE)
-          await pages[0].waitForNavigation();
-        expect(pages[0].url()).toBe(server.EMPTY_PAGE);
+        const page = pages[0];
+        if (page.url() !== server.EMPTY_PAGE)
+          await page.waitForNavigation();
+        expect(page.url()).toBe(server.EMPTY_PAGE);
         await browser.close();
       });
       it('should set the default viewport', async() => {

From 112fd20d6533ee47db9c0fd87c8fd2516ecf4658 Mon Sep 17 00:00:00 2001
From: Mathias Bynens <mathias@qiwi.be>
Date: Wed, 16 Oct 2019 13:15:20 +0200
Subject: [PATCH 6/7] Use an older Node.js that appveyor hopefully supports

---
 .appveyor.yml | 4 ++--
 .travis.yml   | 4 ++--
 package.json  | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/.appveyor.yml b/.appveyor.yml
index 6a2eeff1eb13b..1ec90faa2b4da 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -1,6 +1,6 @@
 environment:
   matrix:
-    - nodejs_version: "8.16.2"
+    - nodejs_version: "8.16.0"
       FLAKINESS_DASHBOARD_NAME: Appveyor Chromium (Win + node8)
   FLAKINESS_DASHBOARD_PASSWORD:
     secure: g66jP+j6C+hkXLutBV9fdxB5fRJgcQQzy93SgQzXUmcCl/RjkJwnzyHvX0xfCVnv
@@ -11,7 +11,7 @@ install:
   - ps: $env:FLAKINESS_DASHBOARD_BUILD_URL="https://ci.appveyor.com/project/aslushnikov/puppeteer/builds/$env:APPVEYOR_BUILD_ID/job/$env:APPVEYOR_JOB_ID"
   - ps: Install-Product node $env:nodejs_version
   - npm install
-  - if "%nodejs_version%" == "8.11.3" (
+  - if "%nodejs_version%" == "8.16.0" (
       npm run lint &&
       npm run coverage  &&
       npm run test-doclint &&
diff --git a/.travis.yml b/.travis.yml
index 86cb12a91e7ec..84f45ce3c4f3b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -26,12 +26,12 @@ script:
   - 'if [ "$NODE8" = "true" ]; then npm run unit-bundle; fi'
 jobs:
   include:
-    - node_js: "8.16.2"
+    - node_js: "8.16.0"
       env:
         - NODE8=true
         - FLAKINESS_DASHBOARD_NAME="Travis Chromium (node8 + linux)"
         - FLAKINESS_DASHBOARD_BUILD_URL="${TRAVIS_JOB_WEB_URL}"
-    - node_js: "8.16.2"
+    - node_js: "8.16.0"
       env:
         - FIREFOX=true
         - FLAKINESS_DASHBOARD_NAME="Travis Firefox (node8 + linux)"
diff --git a/package.json b/package.json
index 618e998facec9..66d31c2d89e44 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "main": "index.js",
   "repository": "github:GoogleChrome/puppeteer",
   "engines": {
-    "node": ">=8.16.2"
+    "node": ">=8.16.0"
   },
   "puppeteer": {
     "chromium_revision": "686378"

From 38a2deab219585b69bea4008c9ef03e52f120dac Mon Sep 17 00:00:00 2001
From: Mathias Bynens <mathias@qiwi.be>
Date: Wed, 16 Oct 2019 14:35:53 +0200
Subject: [PATCH 7/7] Restore helper.promisify so puppeteer-web doesn't break

We can reconsider this once https://github.com/browserify/browserify/pull/1844 gets merged.
---
 .../puppeteer-firefox/lib/BrowserFetcher.js   |  8 ++---
 experimental/puppeteer-firefox/lib/Page.js    |  3 +-
 experimental/puppeteer-firefox/lib/helper.js  | 20 +++++++++++++
 lib/BrowserFetcher.js                         | 10 +++----
 lib/DOMWorld.js                               |  3 +-
 lib/Launcher.js                               |  5 ++--
 lib/Page.js                                   |  3 +-
 lib/helper.js                                 | 29 +++++++++++++++----
 test/launcher.spec.js                         | 11 ++++---
 9 files changed, 63 insertions(+), 29 deletions(-)

diff --git a/experimental/puppeteer-firefox/lib/BrowserFetcher.js b/experimental/puppeteer-firefox/lib/BrowserFetcher.js
index c222754d32584..c7d1250e4c1ee 100644
--- a/experimental/puppeteer-firefox/lib/BrowserFetcher.js
+++ b/experimental/puppeteer-firefox/lib/BrowserFetcher.js
@@ -82,10 +82,10 @@ function downloadURL(product, platform, host, revision) {
   return util.format(downloadURLs[product][platform], host, revision, archiveName(product, platform, revision));
 }
 
-const readdirAsync = util.promisify(fs.readdir.bind(fs));
-const mkdirAsync = util.promisify(fs.mkdir.bind(fs));
-const unlinkAsync = util.promisify(fs.unlink.bind(fs));
-const chmodAsync = util.promisify(fs.chmod.bind(fs));
+const readdirAsync = helper.promisify(fs.readdir.bind(fs));
+const mkdirAsync = helper.promisify(fs.mkdir.bind(fs));
+const unlinkAsync = helper.promisify(fs.unlink.bind(fs));
+const chmodAsync = helper.promisify(fs.chmod.bind(fs));
 
 function existsAsync(filePath) {
   let fulfill = null;
diff --git a/experimental/puppeteer-firefox/lib/Page.js b/experimental/puppeteer-firefox/lib/Page.js
index c2ce1bdb3ed6f..de5c7b41e95f1 100644
--- a/experimental/puppeteer-firefox/lib/Page.js
+++ b/experimental/puppeteer-firefox/lib/Page.js
@@ -4,7 +4,6 @@ const {Dialog} = require('./Dialog');
 const {TimeoutError} = require('./Errors');
 const fs = require('fs');
 const mime = require('mime');
-const util = require('util');
 const EventEmitter = require('events');
 const {createHandle} = require('./JSHandle');
 const {Events} = require('./Events');
@@ -15,7 +14,7 @@ const {TimeoutSettings} = require('./TimeoutSettings');
 const {NavigationWatchdog} = require('./NavigationWatchdog');
 const {Accessibility} = require('./Accessibility');
 
-const writeFileAsync = util.promisify(fs.writeFile);
+const writeFileAsync = helper.promisify(fs.writeFile);
 
 class Page extends EventEmitter {
   /**
diff --git a/experimental/puppeteer-firefox/lib/helper.js b/experimental/puppeteer-firefox/lib/helper.js
index 07f180c7f1be7..92e86ad22b5c6 100644
--- a/experimental/puppeteer-firefox/lib/helper.js
+++ b/experimental/puppeteer-firefox/lib/helper.js
@@ -65,6 +65,26 @@ class Helper {
     }
   }
 
+  /**
+   * @param {function} nodeFunction
+   * @return {function}
+   */
+  static promisify(nodeFunction) {
+    function promisified(...args) {
+      return new Promise((resolve, reject) => {
+        function callback(err, ...result) {
+          if (err)
+            return reject(err);
+          if (result.length === 1)
+            return resolve(result[0]);
+          return resolve(result);
+        }
+        nodeFunction.call(null, ...args, callback);
+      });
+    }
+    return promisified;
+  }
+
   /**
    * @param {!Object} obj
    * @return {boolean}
diff --git a/lib/BrowserFetcher.js b/lib/BrowserFetcher.js
index cea6e3ee97f13..aace9220591f4 100644
--- a/lib/BrowserFetcher.js
+++ b/lib/BrowserFetcher.js
@@ -20,7 +20,7 @@ const path = require('path');
 const util = require('util');
 const extract = require('extract-zip');
 const URL = require('url');
-const {assert} = require('./helper');
+const {helper, assert} = require('./helper');
 const removeRecursive = require('rimraf');
 // @ts-ignore
 const ProxyAgent = require('https-proxy-agent');
@@ -64,10 +64,10 @@ function downloadURL(platform, host, revision) {
   return util.format(downloadURLs[platform], host, revision, archiveName(platform, revision));
 }
 
-const readdirAsync = util.promisify(fs.readdir.bind(fs));
-const mkdirAsync = util.promisify(fs.mkdir.bind(fs));
-const unlinkAsync = util.promisify(fs.unlink.bind(fs));
-const chmodAsync = util.promisify(fs.chmod.bind(fs));
+const readdirAsync = helper.promisify(fs.readdir.bind(fs));
+const mkdirAsync = helper.promisify(fs.mkdir.bind(fs));
+const unlinkAsync = helper.promisify(fs.unlink.bind(fs));
+const chmodAsync = helper.promisify(fs.chmod.bind(fs));
 
 function existsAsync(filePath) {
   let fulfill = null;
diff --git a/lib/DOMWorld.js b/lib/DOMWorld.js
index ba1a3193449d4..c5852cacd9faf 100644
--- a/lib/DOMWorld.js
+++ b/lib/DOMWorld.js
@@ -15,11 +15,10 @@
  */
 
 const fs = require('fs');
-const util = require('util');
 const {helper, assert} = require('./helper');
 const {LifecycleWatcher} = require('./LifecycleWatcher');
 const {TimeoutError} = require('./Errors');
-const readFileAsync = util.promisify(fs.readFile);
+const readFileAsync = helper.promisify(fs.readFile);
 
 /**
  * @unrestricted
diff --git a/lib/Launcher.js b/lib/Launcher.js
index 6a3e4db0463f1..41dc1e5da3ce5 100644
--- a/lib/Launcher.js
+++ b/lib/Launcher.js
@@ -15,7 +15,6 @@
  */
 const os = require('os');
 const path = require('path');
-const util = require('util');
 const http = require('http');
 const https = require('https');
 const URL = require('url');
@@ -31,8 +30,8 @@ const {TimeoutError} = require('./Errors');
 const WebSocketTransport = require('./WebSocketTransport');
 const PipeTransport = require('./PipeTransport');
 
-const mkdtempAsync = util.promisify(fs.mkdtemp);
-const removeFolderAsync = util.promisify(removeFolder);
+const mkdtempAsync = helper.promisify(fs.mkdtemp);
+const removeFolderAsync = helper.promisify(removeFolder);
 
 const CHROME_PROFILE_PATH = path.join(os.tmpdir(), 'puppeteer_dev_profile-');
 
diff --git a/lib/Page.js b/lib/Page.js
index d1cd837bfc400..0bdd217c8291f 100644
--- a/lib/Page.js
+++ b/lib/Page.js
@@ -18,7 +18,6 @@ const fs = require('fs');
 const path = require('path');
 const EventEmitter = require('events');
 const mime = require('mime');
-const util = require('util');
 const {Events} = require('./Events');
 const {Connection} = require('./Connection');
 const {Dialog} = require('./Dialog');
@@ -33,7 +32,7 @@ const {createJSHandle} = require('./JSHandle');
 const {Accessibility} = require('./Accessibility');
 const {TimeoutSettings} = require('./TimeoutSettings');
 
-const writeFileAsync = util.promisify(fs.writeFile);
+const writeFileAsync = helper.promisify(fs.writeFile);
 
 class Page extends EventEmitter {
   /**
diff --git a/lib/helper.js b/lib/helper.js
index 231a148e08803..3c5d987ad0b99 100644
--- a/lib/helper.js
+++ b/lib/helper.js
@@ -16,11 +16,6 @@
 const {TimeoutError} = require('./Errors');
 const debugError = require('debug')(`puppeteer:error`);
 const fs = require('fs');
-const util = require('util');
-
-const openAsync = util.promisify(fs.open);
-const writeAsync = util.promisify(fs.write);
-const closeAsync = util.promisify(fs.close);
 
 class Helper {
   /**
@@ -161,6 +156,26 @@ class Helper {
     return typeof obj === 'number' || obj instanceof Number;
   }
 
+  /**
+   * @param {function} nodeFunction
+   * @return {function}
+   */
+  static promisify(nodeFunction) {
+    function promisified(...args) {
+      return new Promise((resolve, reject) => {
+        function callback(err, ...result) {
+          if (err)
+            return reject(err);
+          if (result.length === 1)
+            return resolve(result[0]);
+          return resolve(result);
+        }
+        nodeFunction.call(null, ...args, callback);
+      });
+    }
+    return promisified;
+  }
+
   /**
    * @param {!NodeJS.EventEmitter} emitter
    * @param {(string|symbol)} eventName
@@ -255,6 +270,10 @@ class Helper {
   }
 }
 
+const openAsync = Helper.promisify(fs.open);
+const writeAsync = Helper.promisify(fs.write);
+const closeAsync = Helper.promisify(fs.close);
+
 /**
  * @param {*} value
  * @param {string=} message
diff --git a/test/launcher.spec.js b/test/launcher.spec.js
index 78fdd93cef1d0..8cb43a9737a42 100644
--- a/test/launcher.spec.js
+++ b/test/launcher.spec.js
@@ -16,12 +16,11 @@
 const fs = require('fs');
 const os = require('os');
 const path = require('path');
-const util = require('util');
-
-const rmAsync = util.promisify(require('rimraf'));
-const mkdtempAsync = util.promisify(fs.mkdtemp);
-const readFileAsync = util.promisify(fs.readFile);
-const statAsync = util.promisify(fs.stat);
+const {helper} = require('../lib/helper');
+const rmAsync = helper.promisify(require('rimraf'));
+const mkdtempAsync = helper.promisify(fs.mkdtemp);
+const readFileAsync = helper.promisify(fs.readFile);
+const statAsync = helper.promisify(fs.stat);
 const TMP_FOLDER = path.join(os.tmpdir(), 'pptr_tmp_folder-');
 const utils = require('./utils');