dist: bionic
language: c
sudo: require
install:
    - sudo add-apt-repository -y ppa:webkit-team/ppa
    - sudo apt-get update
    - sudo apt-get install -y libgtk-3-dev
    - sudo apt-get install -y libwebkit2gtk-4.0-dev
    - sudo apt-get install -y xvfb
    - sudo apt-get install -y metacity
    - sudo apt-get install -y x11-apps
    - sudo apt-get install -y imagemagick
script:
    - make
    - ./test.sh

dist: bionic
language: c
sudo: require
script:
    - make
    - ./test.sh
addons:
    apt:
        update: true
        sources:
            - ppa:webkit-team/ppa
        packages:
            - libwegkit2gtk-4.0-dev
            - libgtk-3-dev
            - xvfb
            - metacity
            - x11-apps # → xwd
            - imagemagick # → convert

Add third-party APT repository for WebKit
Travis: Add third-party APT repository for WebKit

Unlike previous release images, you have to specify these separately:
https://docs.travis-ci.com/user/reference/bionic/#differences-from-the-previous-release-images

I hope I did this correctly.  I have few ways to know but try it.
