Bug 1047275 - Test ellipsis side on RTL pages for FontSizeManager

Add unit tests for testing ellipsis side on RTL pages for FontSizeManager

Also refactor unit tests introduced in Bug 1047998 to prevent repeated code

https://bugzilla.mozilla.org/show_bug.cgi?id=1047275
I am not sure if I get your idea. Let me explain the purpose of `viewElements`.
Original test cases test `div` element and examine its `textContent`. However, in dialer, what we really use to display is an `input` element. That's what bug 1047998 is fixing. So I added more test cases for it but basically these new test cases are almost the same as original ones (just assert on `value` instead of `textContent`). And I thought it'd better to group them together.