Merge from Widevine repo of http://go/wvgerrit/68464
The Full Decrypt Path Testing design has changed to remove
OEMCrypto_InitializeDecryptHash. This CL updates the unit tests and
reference code.
Bug: 120795057
Test: unit tests
Change-Id: Iee28fa9034dc21cee81c5b894c192e260375eeee