BrowserMob proxy at http://bmp.lightbody.net/ captures network traffic into HTTP Archive Report (HAR) files containing measurements of time to load elements on the page. There are several precise points in time that can be measured:
The forum for this is at https://groups.google.com/forum/#!forum/browsermob-proxy
Files are sent to LogStash.