title: Please, set "CHROME_BIN" env variable inside docker npm test
body: <p>'npm run test' works completely fine on the server or on my local but its failing on my docker machine. I am bit new to this docker world so I am just confused about whats going wrong here.
  I was getting the error: </p>
  
  <pre><code>Post stage
  [32m15 07 2018 18:41:35.164:INFO [karma]: [39mKarma v1.2.0 server started at http://localhost:9876/
  [32m15 07 2018 18:41:35.169:INFO [launcher]: [39mLaunching browser ChromeHeadless with unlimited concurrency
  [32m15 07 2018 18:41:35.185:INFO [launcher]: [39mStarting browser ChromeHeadless
  [31m15 07 2018 18:41:35.186:ERROR [launcher]: [39mNo binary for ChromeHeadless browser on your platform.
    Please, set "CHROME_BIN" env variable.
  
  Finished in 0 secs / 0 secs @ 18:41:35 GMT+0000 (UTC)
  
  npm ERR! code ELIFECYCLE
  </code></pre>
  
  <p>Somewhere I found that, it might be missing chrome.. so I installed chrome manually inside my docker:</p>
  
  <pre><code># install manually all the missing libraries
  RUN apt-get install -y gconf-service libasound2 libatk1.0-0 libcairo2 libcups2 libfontconfig1 libgdk-pixbuf2.0-0 libgtk-3-0 libnspr4 libpango-1.0-0 libxss1 fonts-liberation libappindicator1 libnss3 lsb-release xdg-utils
  
  # install chrome
  RUN wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb
  RUN dpkg -i google-chrome-stable_current_amd64.deb; apt-get -fy install
  </code></pre>
  
  <p>Then I set the chrome environment variable inside the docker using:
  export CHROME_BIN=/usr/bin/google-chrome</p>
  
  <p>But still when I run npm test, it fails with this error:</p>
  
  <pre><code>15 07 2018 19:20:46.291:INFO [launcher]: Starting browser ChromeHeadless                                                                        15% building modules 45/51 modules 6 active ...iv2/node_modules/zone.js/dist/zone.js15 07 2018 19:20:46.964:ERROR [launcher]: Cannot start ChromeHeadless
                                                                           19% building modules 79/79 modules 0 active15 07 2018 19:20:47.750:INFO [launcher]: Trying to start ChromeHeadless again (1/2).                                                                       20% building modules 84/90 modules 6 active ...ode_modules/webpack/buildin/global.js15 07 2018 19:20:48.097:ERROR [launcher]: Cannot start ChromeHeadless
                                                                           20% building modules 91/98 modules 7 active ...node_modules/angular2-moment/index.js15 07 2018 19:20:48.166:INFO [launcher]: Trying to start ChromeHeadless  22% building modules 103/156 modules 53 active ...s/rxjs/_esm5/operator/timeInterval.js15 07 2018 19:20:49.199:ERROR [launcher]: Cannot start ChromeHeadless
                                                                        23% building modules 110/181 modules 71 active ...amic/esm5/platform-browser-dynamic.js15 07 2018 19:20:50.050:ERROR [launcher]: ChromeHeadless failed 2 times (cannot start). Giving up.
  
  Finished in 0 secs / 0 secs @ 19:20:50 GMT+0000 (UTC)
                                                                        23% building modules 111/185 modules 74 active ...e_modules/angular2-cookie/services.js
  </code></pre>
  
  <p>Anyone has any idea how I can solve this. Please note, this is happening inside my docker and my base docker image is 'python:2.7.13-slim'</p>