need better way of tracking video performance

Currently we track media performance using "draw fps" - by tracking the time when a frame is being rendered.

This is misleading and may not represent user's experience since if we're late delivering a new frame we may just re-render the same frame resulting in unsmooth video appearance.

Possible metrics to track:
  - lag between when frame is supposed to be delivered by decoder vs when it was actually delivered
  - lag between frames delivered by the decoder vs when they are painted
  - 'decoding fps', 'rendering fps'
  - video-audio synchronization
  - video quality

Attached is a Java app which tracks some of these metrics.