[automerger] M3UParser: detect variant streams without EXT-X-STREAM-INF am: f3e0afb82f am: 4b29913d94 am: a6bd71fcb8 am: 1816776c89 am: 86eb461699 am: e31e750544

Change-Id: Ie94b060cdb7633e6b6f3640a6e2b5b984b3d1361