ci: use Chrome addon (#122)

.travis.yml

@@ -4,13 +4,12 @@ node_js:
   - "10"
 env:
   - BACKEND_CPU=true EXCLUDE_UNCOMPRESSED=true
-before_script:
-  - wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
-  - sudo sh -c 'echo "deb http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list'
-  - sudo apt-get update
-  - sudo apt-get install google-chrome-stable
-  - export DISPLAY=:99.0
-  - sh -e /etc/init.d/xvfb start
+addons:
+  chrome: stable
+before_install:
+ - export DISPLAY=:99.0
+ - sh -e /etc/init.d/xvfb start
+ - sleep 3 # give xvfb some time to start
 script:
   - npm run test-travis
   - npm run build
\ No newline at end of file