[CommonHTML] Passing ARIA roles through

The CommonHTML does not pass roles "perfectly". For example, a role=presentation on an mi will not make it to the actual content node but a wrapping element (thus not having the desired effect of hiding the node with the mi's content from AT).

[This is probably just extremely minor. I'm not sure if there are any serious repercussions of this (any roles that are really problematic). Just wanted to make a note.]