apprtc: add &ssr=1 for stereoscopic render (e.g. Oculus Rift).
(local preview during the call is removed in this mode)

Remember to double-click the remote view canvas to full-screen it!
Merge branch 'vikas_e2e_RTT'

Add RTT and delay stats to the info div.
Use optional constraints for HD default.

If HD is not explicitly specified, make the track constraints optional
instead of mandatory, so that we work with non-HD cameras.
Fix bug where the video= URL param no longer worked.
Document new constraints behavior in comments
Don't transition to active until video starts.

Workaround a Chrome issue, where we don't fire onaddstream before the
SetRD success callback.
https://code.google.com/p/webrtc/issues/detail?id=3358
Also, fix a few logging issues.