Bug 1082139 - JavascriptException: JavascriptException: TypeError: window.getComputedStyle(...) is null at: app://callscreen.gaiamobile.org/gaia_build_defer_index.js line: 146

Checking this is not robust enough. If we get rid of calls to it, these tests will continue to pass. We should instead set up a scenario where we know that ```FontSizeManager.adaptToSpace()``` will set a different font size, as in other tests in this file. We should then check that the font size doesn't change.