1. Similar to 880f3d8, don't consider not getting an output buffer as
an error during flushing. I've seen the following sometimes when
encoding:
W GStreamer+amcvideoenc: java.lang.IllegalStateException
W GStreamer+amcvideoenc: at android.media.MediaCodec.getBuffer(Native Method)
W GStreamer+amcvideoenc: at android.media.MediaCodec.getOutputBuffer(MediaCodec.java:2886)
2. For amcvideodec/enc, call _find_nearest_frame (which grabs a fresh
reference on a GstVideoCodecFrame) after we have an output buffer,
so as to not leak the reference, in case getting an output buffer
fails.
Otherwise, if we get an error grabbing the output buffer, we leak
the reference to the frame. This can cause issues with a
v4l2bufferpool feeding the encoder not being able to clean itself
up properly due to buffers still being marked as in-use.
https://bugzilla.gnome.org/show_bug.cgi?id=791258
236398ee3f