fate/ffmpeg: add test for time limited sub2video instance

Utilizes a subpicture sample with one decodable subpicture for the
test.

Based on a failing test case in reported by Michael in
https://ffmpeg.org/pipermail/ffmpeg-devel/2019-February/240398.html
which at the time had no test case for it.

Additionally, this is the first test case for the presentation
graphics format.

tests/fate/ffmpeg.mak

@@ -65,6 +65,16 @@ fate-sub2video_basic: CMD = framecrc \
   -filter_complex "sws_flags=+accurate_rnd+bitexact\;[0:s:0]scale" \
   -c:v rawvideo
 
+# Time-limited run with a sample that doesn't require seeking and
+# contains samples within the initial period.
+FATE_SAMPLES_FFMPEG-$(call ALLYES, SUP_DEMUXER PGSSUB_DECODER AVFILTER) += fate-sub2video_time_limited
+fate-sub2video_time_limited: CMD = framecrc \
+  -i $(TARGET_SAMPLES)/sub/pgs_sub.sup \
+  -vsync passthrough -copyts \
+  -t 15 \
+  -filter_complex "sws_flags=+accurate_rnd+bitexact\;[0:s:0]scale" \
+  -c:v rawvideo
+
 FATE_FFMPEG-$(call ALLYES, PCM_S16LE_DEMUXER PCM_S16LE_MUXER PCM_S16LE_DECODER PCM_S16LE_ENCODER) += fate-unknown_layout-pcm
 fate-unknown_layout-pcm: $(AREF)
 fate-unknown_layout-pcm: CMD = md5 \

tests/ref/fate/sub2video_time_limited

+#tb 0: 1/25
+#media_type 0: video
+#codec_id 0: rawvideo
+#dimensions 0: 1920x1080
+#sar 0: 0/1
+0,          2,          2,        1,  8294400, 0x00000000
+0,          2,          2,        1,  8294400, 0xa87c518f
+0,         10,         10,        1,  8294400, 0xa87c518f