Save the value of the pad's got_eos in gst_funnel_release_pad,
before calling gst_element_remove_pad. This is because
gst_element_remove_pad may free the pad.
https://bugzilla.gnome.org/show_bug.cgi?id=678017
If multiple sources are plugged into the funnel and one of the
sources emits an EOS, that event is propogated through the funnel
even though other sources connected to the funnel may still be
pushing data. This patch waits to send an EOS event until the
funnel has received an EOS event on each sinkpad.
1) We need to lock and get a strong ref to the parent, if still there.
2) If it has gone away, we need to handle that gracefully.
This is necessary in order to safely modify a running pipeline. Has been
observed when a streaming thread is doing a buffer_alloc() while an
application thread sends an event on a pad further downstream, and from
within a pad probe (holding STREAM_LOCK) carries out the pipeline plumbing
while the streaming thread has its buffer_alloc() in progress.
