Loader#headers

Used to map the application mime-types to to the Accept header in XHR requests.
If you don't require these mappings, or they cause problems on your server, then
remove them from the headers object and the XHR request will not try to use them.

This object can also be used to set the X-Requested-With header to
XMLHttpRequest (or any other value you need). To enable this do:

this.load.headers.requestedWith = 'XMLHttpRequest'

before adding anything to the Loader. The XHR loader will then call:

setRequestHeader('X-Requested-With', this.headers['requestedWith'])