Add support for Chromecast variant of PlayReady
Add support for Chromecast variant of PlayReady

Chromecast has a variant of PlayReady that uses a different key system
ID.

In addition to mapping between key system IDs and making other small
exceptions for Chromecast, I also fixed a bug in the calculation of
expired key statuses.  The ChromeCast PlayReady implementation does
not expose key status information at all, and this caused us to
erroneously declare all keys expired.

Change-Id: I52c96eec0040af6bf902a614760b8cd06e608dcd

indiereign/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,TheModMaker/shaka-player,russitto/shaka-player,TheModMaker/shaka-player,russitto/shaka-player,russitto/shaka-player,tvoli/shaka-player,vimond/shaka-player,indiereign/shaka-player,vimond/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,TheModMaker/shaka-player,tvoli/shaka-player,indiereign/shaka-player,vimond/shaka-player,TheModMaker/shaka-player