Bug 1071009 - [Loop] Expose bitrate, frames dropped and frame delay to a...

...pplications via TB library.
Added all information given by tokbox including framerate on encoder/decoder side, frames dropped and bitrate. RTP information also available.
Tokbox doesn't provide framedelay information. That info must be retrieved from gecko.
for (var key in stats) {
  if (stats.hasOwnProperty(key)) {
    doSomething
}
}
is the same, but more verbose than:

Object.keys(stats).forEach(function(key) {
  doSomething
}

And, on the other hand, if stats doesn't inherit from anything or it's build from a prototype then you can just remove the hasOwnProperty call.