Fix replaying of content in Firefox

[LloydW93]

Steps to reproduce issue:

1. Start playing an MPD longer than a couple of minutes, such that early buffer is purged
2. Seek to a few seconds before the end (or play naturally through)
3. Wait for content to end
4. Click play again

Expected behaviour:
Playback restarts from the beginning of the media

Actual behaviour:
Playback never starts

[LloydW93]

Sorry, think I managed to miss this comment.

I've just tried the sample MPDs above with this branch in Firefox and Chrome:

1. 👍
2. Firefox: Playback stops 1-3 seconds before the end. Happens in DASH-IF development branch too.
3. Firefox: Playback stops after a few seconds. Happens in DASH-IF development branch too.
4. 👍
5. 👍
6. 👍
7. 👍

None of the streams with captions in FF show the CC option in the UI so there is no way to verify them.

[cpeterso]

mpd 2 and 3 play correctly for me with Firefox 43–46 on OS X 10.11 and Windows 10.

[dsparacio]

http://vm2.dashif.org/livesim-dev/utc_direct-head/testpic_2s/Manifest.mpd Can you test this as well.

No UI for CC means not text tracks added to video element which means there is either an issue with TextTracks in Firefox... Ill check it out today

[cpeterso]

I don't think timed text captions are supported in Firefox.

[dsparacio]

@cpeterso we manually handle all of that as it is not supported by MSE in any browser at this time. It is a simple function on the video element. We parser and create tracks and append to element track list.

[dsparacio]

I am going to pull this in but seems like needs a rebase. Please do and Ill pull in and test TT stuff.

[LloydW93]

Clean and now ready to merge.

Lost the MPD list comment:

I can't remember why this was here but it was here for something very specific and now that it has been removed I am not sure what it will break but pretty sure it will break something ;) I think fragmented text tracks... How many content permutations did you test after you removed this line?

Here are a few streams with text tracks that I have been smoke testing with. May help.

http://vm2.dashif.org/livesim-dev/testpic_2s/Manifest.mpd
http://vm2.dashif.org/dash/vod/testpic_2s/multi_subs.mpd
http://vm2.dashif.org/livesim-dev/testpic_2s/multi_subs.mpd
http://wams.edgesuite.net/media/MPTExpressionData02/BigBuckBunny_1080p24_IYUV_2ch.ism/manifest(format=mpd-time-csf)
http://vm2.dashif.org/livesim-dev/modulo_10/testpic_2s/Manifest.mpd
http://dash.edgesuite.net/akamai/test/caption_test/ElephantsDream/elephants_dream_480p_heaac5_1.mpd
http://vm2.dashif.org/livesim-dev/periods_20/testpic_2s/Manifest.mpd

[dsparacio]

@cpeterso @LloydW93 So this is interesting my comment on video element and adding tracks vs source buffer support via MSE for Timed Text may not be accurate. Seems like the issue si in firefox on the video element itself. It is not allowing us to add tracks. So like IE we may need a special work around for this. I will file a new bug.