This is a new flag, proposed for the XHR object, that tells the browser to make an anonymous request.
We should support this in some way as an AjaxProperties flag, and also map it to mozAnon and mozSystem for Firefox OS support.
all (esp Firefox OS)
So mozSystem is dependent on mozAnon being true, but is the converse necessarily true? Not sure if we need to link the XHR anon attribute to both mozAnon and mozSystem, instead of just mozAnon. But at the same time, not sure which standard XHR attribute would be mapped to mozSystem to allow setting this in a more generic way.