add headless chrome browser option for UI only tests

[toschneck]

Like described on Google Dev Blog Chrome 59+ supports a headless mode. Due to this fact we can us this for "UI only" tests with Sakuli.

Solution:

• configure the browser configuration of sahi like in the attached linux.xml
• user as browser chrome_headless

  FROM consol/sakuli-ubuntu-xfce:v1.1.0
  COPY linux.xml $SAKULI_ROOT/sahi/config/browser_types/
  ENV TESTSUITE_BROWSER=chrome_headless

  <browserTypes>
  ....
  <browserType>
      <name>chrome_headless</name>
      <displayName>Chrome Headless</displayName>
      <icon>chrome.png</icon>
      <path>/usr/bin/google-chrome</path>
      <options>--incognito --headless --disable-gpu --remote-debugging-port=9222 --user-data-dir=$userDir/browser/chrome/profiles/sahi$threadNo --start-maximized --no-default-browser-check --no-first-run --disable-infobars --proxy-server=localhost:9999 --disable-popup-blocking</options>
      <processName>chrome</processName>
      <capacity>5</capacity>
  </browserType>
  </browserTypes>

TODO:

• Add chrome_headless as additional browser like firefox_portable
• Add Documentation