Start getting PhantomJS working for tests

PhantomJS is nice because it is headless so:
1.  It is just a tiny bit faster than Firefox
2.  It can be run in parallel no problem.
3.  It never steals focus so REUSE_BROWSER is no longer tempting.
4.  It can be run more easilly on Jenkins.

Change-Id: I17c5788eac4e9822dee910c6e6eb654ea60e50e0
Merge "Start getting PhantomJS working for tests"