Legacy players, e.g. older versions of ExoPlayer, do not handle default webvtt text alignment correctly. Need to specify `align:center` explicitly cues without text alignment for backwards compatibility.
Fixes#925.
Now the same pipeline for handling the audio/videos streams will handle
the segmented text streams too. This doesn't apply to the text output,
only to the MP4 variants. This also fixes a bug where we added the
X-TIMESTAMP-MAP tag even when there wasn't TS streams; this doesn't
otherwise change the behavior around that tag.
Change-Id: I03f7cea56efa42e96311c00841330629a14aa053
This changes it from an OriginHandler to a MediaParser and moves the
handling of it to the Demuxer. This will allow more generic handling
of text by giving it the same abstractions as video/audio handling.
Change-Id: Ibbde3c84d228ec8e83af1ed266ea97dbc9589c24