Use chrome 48.

This upgrade is in tandem with browser-testing upgrades on edx-platform. The
jenkins_worker role relies on the browser role when creating new workers. This
means that a given jenkins worker would have chrome 48 installed on it, and
that this would be used for tests.

playbooks/roles/browsers/defaults/main.yml

@@ -12,11 +12,11 @@ browser_deb_pkgs:
 # Both Chrome and FireFox update their apt repos with the latest version,
 # which often causes spurious acceptance test failures.
 browser_s3_deb_pkgs:
-    - { name: "google-chrome-stable_30.0.1599.114-1_amd64.deb", url: "https://s3.amazonaws.com/vagrant.testeng.edx.org/google-chrome-stable_30.0.1599.114-1_amd64.deb" }
+    - { name: "google-chrome-stable_30.0.1599.114-1_amd64.deb", url: "https://s3.amazonaws.com/vagrant.testeng.edx.org/google-chrome-48.0_amd64.deb" }
     - { name: "firefox_28.0+build2-0ubuntu0.12.04.1_amd64.deb", url: "https://s3.amazonaws.com/vagrant.testeng.edx.org/firefox_28.0%2Bbuild2-0ubuntu0.12.04.1_amd64.deb" }
 
 # Chrome and ChromeDriver
-chromedriver_version: 2.6
+chromedriver_version: 2.21
 chromedriver_url: "http://chromedriver.storage.googleapis.com/{{ chromedriver_version }}/chromedriver_linux64.zip"
 
 # PhantomJS