W3C Resource Timing API: Easy access to timing information for a particular XmlHttpRequest

I don't believe the Resource Timing API
<http://www.w3.org/TR/resource-timing/> includes a 100% clean method for
getting the timing information corresponding to an XmlHttpRequest object.
If this is the case, it might help users to include a simple lookup as part
of the API.

My use case:
I'd like to get request timing information for a particular XmlHttpRequest
so I can set timeouts for various stages of the request.  For example, I
don't want my network timeout budget to include time spent waiting for
other, unrelated connections to finish.

It seems I can use the URL being requested with
window.performance.getEntriesByName.  However, if there are multiple
requests to the same URL, I don't know of a 100% reliable way of matching
my XmlHttpRequest object up with the returned entries.  Perhaps it's
possible by using the workerStart timestamp, but if so that seems clumsy.

Thanks,
Red