Merge from master branch of Widevine repo of http://go/wvgerrit/66074
Merge from oemcrypto-v15 branch of Widevine repo of http://go/wvgerrit/65102
Currently, the string only contains the mac_key_server, which isn't an
issue currently because we just get the offset into the message for the
enc_mac_keys pointer when calling LoadKeys, and rely on OEMCrypto to
read the 64 bytes. However, v15 will need the length of the enc_mac_keys
to reflect the true size.
Test: tested as part of http://go/ag/5501993
Bug: 115874964
Change-Id: Id76e91feb176755467c0433e6b0e87d2bb221033