Also removes OnSessionExpiration which is no longer needed with
OnSessionKeysChange.
Bug: 19771612
Bug: 19771431
Merged from Widevine CDM repo:
https://widevine-internal-review.googlesource.com/#/c/13951/
Change-Id: I0603e808e8d50ff7bb1fb1d5e44fabd8d268ee8a