MSE: Recognize "unknown duration" in ISOBMFF mvhd version 0, duration max uint32 case

media/test/data/README

Index: media/test/data/README
diff --git a/media/test/data/README b/media/test/data/README
index 89466e060d38804cfceec8d6150ed7c6aef26f1a..3d752bd0dca90a2e9a7a7de8cc53eb7458227bad 100644
--- a/media/test/data/README
+++ b/media/test/data/README
@@ -11,6 +11,10 @@ bear-vp8-webvtt.webm - WebM VP8 video with WebVTT subtitle track.
 bear-1280x720_avt_subt_frag.mp4 - Fragmented bear_1280x720.mp4 with text track
                                   containing srt from bear-vp8-webvtt.webm as
                                   a 'subt' handler type.
+bear-1280x720_av_frag.mp4 - Fragmented bear_1280x720.mp4.
+bear-1280x720_av_frag-initsegment-mvhd_version_0-mvhd_duration_bits_all_set.mp4:
+  Just the first initialization segment of bear-1280x720_av_frag.mp4, modified to
+  have the mvhd version 0 32-bit duration field set to all 1's.
 bear-vp8a.webm - WebM VP8 video with alpha channel.
 bear-vp8a-odd-dimensions.webm - WebM VP8 video with alpha channel and odd dimensions.
 bear-opus.webm - Opus Audio only WebM file.