test(compileSpec): fix broken build on FF

FF 26.0 now throws:

"TypeError: NodeList doesn't have an indexed property setter."

when we try to assign to `childNodes[1]`, since this test still works properly
on Chrome and the issue being tested is not a cross-browser issues, I'm
just making the patchability check more robust instead of trying to figure
out how to make this test fully pass on FF.