Use Docker containers in Travis (ampproject#9666)

.travis.yml

@@ -1,6 +1,6 @@
 language: node_js
-sudo: required  # See http://docs.travis-ci.com/user/trusty-ci-environment/
 dist: trusty
+sudo: false  # See http://docs.travis-ci.com/user/trusty-ci-environment/
 node_js:
   - "4"
 python:
@@ -21,11 +21,12 @@ addons:
     - protobuf-compiler
     - python-protobuf
 before_install:
-  - export CHROME_BIN=google-chrome
   - export DISPLAY=:99.0
   - sh -e /etc/init.d/xvfb start
   - wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb
-  - sudo dpkg -i google-chrome*.deb
+  - mkdir "${TRAVIS_BUILD_DIR}/chrome"
+  - dpkg -x google-chrome-stable_current_amd64.deb "${TRAVIS_BUILD_DIR}/chrome"
+  - export CHROME_BIN="${TRAVIS_BUILD_DIR}/chrome/opt/google/chrome/google-chrome"
 before_script:
   - pip install --user protobuf
   - gem install percy-cli