aggregator: keep chain functions as dumb as possible.
aggregator: keep chain functions as dumb as possible.

+ A pad chain function has no business checking other pads,
  that's what the aggregate thread is for.

https://bugzilla.gnome.org/show_bug.cgi?id=742684

StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer