[chromedriver] Hardcode mobile devices list.

Previously chromedriver generated the mobile devices list from OverridesUI.js in Blink, however changes introduced in Blink revision 177868 break our tests. I'm hardcoding the value of our mobile devices list to what is was prior to this Blink change, until we implement a new way to generate the list.

BUG=392430

Review URL: https://codereview.chromium.org/390513002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@283354 0039d316-1c4b-4281-b951-d872f2087c98