Aggregator should not encourage direct GstElement->sinkpads access
The GstAggregator docs encourage sub-classes to directly iterator the GstElement->sinkpads list, which is dangerous to do without holding the GST_OBJECT_LOCK(), as request pads could be added or removed at any time.
It would be better to encourage (and provide examples of) using gst_element_iterate_sink_pads()
instead.