Network performance measurement CORS improvements

- Fixes feature check for IE6 and older browsers without native XHR
- Skip crossOrigin attribute for IE11 because it prevents caching

Change-Id: I99d6a3c97edac1af12750d5978a84b6e6f631b14
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/232/
Merge "Network performance measurement CORS improvements"