http://dev.w3.org/csswg/cssom-view/ The most recent W3 standards (which I know is currently on RFC) on the viewport model implies that 
> they can be implemented by all browsers in an interoperable manner
so I read this as an implication that all browsers also includes mobile and so this shouldn't be an issue? Provided of course the implication is correct and that all browsers heed the API spec, but for the major browsers compliance shouldn't be an issue.