Bug 1088271 - Give CustomDialog text it's own span

https://bugzilla.mozilla.org/show_bug.cgi?id=1088271
so, I can, but then I have to set up mediaapp and sound options for the whole suite with other tests. Having my own suite for this test means that I can isolate the environment and set it up before the test.

Let me know if you're ok with me keeping it as a separate suite.