Fix annotations in MediaReadyState util
Fix annotations in MediaReadyState util

For some reason, the new compiler in the master branch let this by,
but the old compiler in the v2.5.x branch complained when I
cherry-picked the utility.

Change-Id: I1e688f72594b74ed7d2a7c2801eb179b8ec13e8c

tvoli/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player