Protractor issue #1895 - Cannot start webdriver as a process

foo.js

module.exports = function (grunt) {
  grunt.registerMultiTask('foo', 'foo bar baz', function () {
    var done = this.async()

    var webdriver = grunt.util.spawn({
      opts: { stdio: 'pipe' },
      cmd: 'node',
      args:['./node_modules/.bin/webdriver-manager', 'start']
    })
    webdriver.stdout.pipe(process.stdout)
    webdriver.stderr.pipe(process.stderr)

    function runProtractor() {
      var ptor = grunt.util.spawn({
        opts: { stdio: 'pipe' },
        cmd: 'node',
        args: ['./node_modules/.bin/protractor', '--seleniumAddress', 'http://localhost:4444/wd/hub', '--specs', 'tspec.js', '--browser', 'firefox']
      },
      function(error, result, code) {
        done()
      })

      ptor.stdout.pipe(process.stdout)
      ptor.stderr.pipe(process.stderr)
    }

    var webdriverStarted = false
    webdriver.stderr.on('data', function(data) {
      if (!webdriverStarted && (data && data.toString().match(/Started .*Server/))) {
        webdriverStarted = true
        runProtractor()
      }
    })
  })
}

Gruntfile.js

module.exports = function(grunt) {
  grunt.initConfig({
    foo: {
      bar: {
       options: {}
      }
    }
  })
  
  grunt.loadTasks('tasks')
  grunt.registerTask('default', ['foo'])
}

package.json

{
  "name": "tmp",
  "version": "1.0.0",
  "description": "",
  "main": "proc.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "MIT",
  "dependencies": {
    "grunt": "^0.4.5",
    "grunt-cli": "^0.1.13",
    "protractor": "1.8.0"
  }
}

proc.js

var spawn = require('child_process').spawn
var webdriver

(function runWebdriver() {
  webdriver = spawn('node', ['./node_modules/.bin/webdriver-manager', 'start'])
  webdriver.stdout.pipe(process.stdout)
  webdriver.stderr.pipe(process.stderr)
})()

function runProtractor() {
  var ptor = spawn('node', ['./node_modules/.bin/protractor', '--seleniumAddress', 'http://localhost:4444/wd/hub', '--specs', 'tspec.js', '--browser', 'firefox'])
  ptor.stdout.pipe(process.stdout)
  ptor.stderr.pipe(process.stderr)
}

var webdriverStarted = false
webdriver.stderr.on('data', function(data) {
  if (!webdriverStarted && (data && data.toString().match(/Started .*Server/))) {
    webdriverStarted = true
    runProtractor()
  }
})

tspec.js

describe('it', function() {
  beforeEach(function() {
    browser.get('https://www.angularjs.org')
  })

  it('should sleep', function() {
    browser.sleep(1000)
  })
})