coverage doesn't include service worker js reduced test case

package.json

{
  "name": "pupeteer-service-worker-coverage-test",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "bin": {
    "b48a0022dbef999f241881f80d7575a9": "./service-worker-test.js"
  },
  "author": "Ryan Day",
  "license": "MIT",
  "bugs": {
    "url": ""
  },  
  "homepage": "",
  "dependencies": {
    "puppeteer": "^1.1.0"
  }
}

service-worker-test.js

#!/usr/bin/env node
'use strict'
//"puppeteer": "^1.1.0",
const puppeteer = require('puppeteer')
const http = require('http')

// browser js to register service worker.
const setupjs = `
  navigator.serviceWorker.register('/worker',{scope:"/"}).then((reg)=>{
    window.swinstalled = true
    console.log('install successful')
  }).catch((e)=>{
    window.swinstalled = false
    console.log('install failed.',e)
  })
`

// the actual service worker.
const worker = `
  self.addEventListener('install', function(event) {
      event.waitUntil(self.skipWaiting());
  });

  self.addEventListener('activate', function(event) {
      event.waitUntil(self.clients.claim());
  });

  self.addEventListener('fetch', event => {
    event.respondWith(new Response("response from worker!", {headers: {'Content-Type': 'application/json'}}))
  })

`

// create an http server to serve index and the worker.
var server = http.createServer(function (req, res) {
  if (req.url === '/worker') {
    res.setHeader('content-type', 'application/javascript')
    return res.end(worker)
  }

  res.setHeader('content-type', 'text/html')
  res.end('index <script>' + setupjs + '</script>')
})

server.listen(0, async function (err) {
  if (err) throw err

  const address = 'http://localhost:' + this.address().port

  const browser = await puppeteer.launch()
  const page = await browser.newPage()

  await page.coverage.startJSCoverage()
  await page.goto(address)

  // wait for sw to be installed
  await page.waitForFunction('window.swinstalled !== undefined')

  const res = await makeRequest(page, '/should-hit-worker')

  console.log(res.body === 'response from worker!', 'should be response from service worker.')

  const coverage = await page.coverage.stopJSCoverage()

  console.log('=== coverage ===')
  console.log(JSON.stringify(coverage, null, '  '))

  await browser.close()
  server.unref()
})

//
// wrap up the fetch api so its easier to call through puppeteer
async function makeRequest (page, path) {
  var id = Date.now() + '' + Math.random()

  await page.evaluate(`
    fetch(${JSON.stringify(path || '')}).then((res)=>{
      var method = res.method
      var status = res.statusCode
      var headers = [...res.headers]
      res.text().then((body)=>{
        window["${id}"] = [null,{method,status,headers,body}]
      }).catch((e)=>{
        window["${id}"] = [e+''] 
      })
    }).catch((e)=>{ 
      window["${id}"] = [e+''] 
    })
  `)

  await page.waitForFunction(`window["${id}"] !== undefined`)

  var res = await page.evaluate(`JSON.stringify(window["${id}"])`)

  res = JSON.parse(res)
  if (res[0]) throw new Error(res[0])
  return res[1]
}

process.on('unhandledRejection', e => { console.log(e); process.exit(1) })