Use provider XHR information in performance metrics + several fixes

* more robust method of obtaining URL
* decouple performance logging from providers (mostly)
* ignore fake XHR object which jQuery returns for JSONP requests
* guard for CORS requests - apparently Chrome refuses to return
  certain information even with an Allow-Origin: * response header.
* Resource Timing is limited to 150 results, which causes fake
  misses in debug mode. There is an API to increase the limit
  but it is not implemented in Chrome. I am calling it nevertheless,
  maybe IE understands it (it is present in the MSDN docs at least).

This seems to work for AJAX, CORS, JSONP, image AJAX; CORS requests
return 0 for a lot of values, per spec a Timing-Allow-Origin: *
header might help that.

Change-Id: I8353858022f51a7e70774e65513d0fa2554a5064