tests: Bump to latest version of chromedriver

.travis.yml

@@ -28,8 +28,8 @@ env:
 before_install:
     - export DISPLAY=:99.0
     - sh -e /etc/init.d/xvfb start
-    - curl -Lo chrome.zip https://download-chromium.appspot.com/dl/Linux_x64 && unzip chrome.zip
-    - curl -Lo chromedriver.zip http://chromedriver.storage.googleapis.com/2.18/chromedriver_linux64.zip && unzip chromedriver.zip
+    - curl -Lo chrome.zip https://download-chromium.appspot.com/dl/Linux_x64?type=continuous && unzip chrome.zip
+    - curl -Lo chromedriver.zip http://chromedriver.storage.googleapis.com/2.20/chromedriver_linux64.zip && unzip chromedriver.zip
 script:
     # We want to gate on passing tests and a successful build
     - ./test-runner.sh