Use xvfb service

Author: Patrick Walsh

.travis.yml

@@ -11,6 +11,8 @@ cache:
   directories:
   - node_modules
 sudo: false
+services:
+  - xvfb
 install:
 - npm -g install npm@5.10
 - npm install

travis_tests.sh

@@ -4,9 +4,6 @@ set -ev
 if [ "${TEST_SUITE}" = "browser" ]; then
   # Load display for browser tests
   export DISPLAY=:99.0
-  sh -e /etc/init.d/xvfb start
-  # give xvfb some time to start
-  sleep 3 
   npm run build
   npm run test:browser
 else