Add totalPageLoadTime (navStart to loadEventEnd) to Ganglia

Adds an additional graph to the Navigation Timing view in Ganglia, showing the
total time from the start of navigation to the end of the window.onload event.

Change-Id: Ibb1eaf49846012a8f670e6576fc4dd05b4db63e4
Merge "Add totalPageLoadTime (navStart to loadEventEnd) to Ganglia" into production