1. Currently, we may throw source info refresh errors while the previous media
period is still playing.
2. We don't throw if the next period in a playlist fails to prepare and the
previous renderers are all disabled.
3. We throw source info refresh errors for playlists before playback reaches
the culprit source.
This change:
1. Defers the exceptions until all existing media periods have been played.
2. Checks for period preparation exception if the next period is not
getting prepared and the renderer time reached the next period.
3. Does no longer throw from ConcatenatingMediaSource.maybeThrowSourceInfo
RefreshError. The deferred media periods take care of that for each source
individually.
Issue:#4661
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=211819436
67a2bb3d28