Anyway to load xml content instead of url in Google maps XMLHttpRequest object?

Since the object requires an URL as an argument to load the XML, how do I pass a string variable with XML content into it?

From here:

function downloadUrl(url,callback) {
...
}

The variable in JavaScript:

>xmlData
"<?xml version="1.0"?><markers>...</markers>"

I know I can save the XML file using the DOM method save(), but at present I seem to be having permission issues at the server I am deploying.