Getting size size with playbin2

[Nikos Chantziaras]

There doesn't seem to be a direct way to get the video size (its 
resolution, not byte size) in GStreamer.  I'm not sure how to do this. 
It seems I have to watch for some signal from the pipeline (I'm using 
playbin2) which is emitted when that information becomes available.  But 
which signal?  And once it's emitted, how do I extract that information?

It all seems awfully round-about for such a simple operation, and it's 
not clear at all how to proceed with this.  Any hints?

I'm on GStreamer 0.10.36.