Bug 916904. Add suitable prefs for image visibility for metro and enable image visibility on metro. r=jimm

The default state of image visibility is enabled, so that just makes that explicit, but we also give good values for the parameter prefs of image visibility.
Bug 904617: Part 1 - Add a way to get cube latency, add wasapi latency functions r=kinetik
Bug 904617: Part 2 - Expose Audio Stream Latency r=padenot,jesup
Bug 904617: Part 3 - Log latency, and adds a python script to understand the log r=padenot,jesup,ehugg