The errors in the range ERROR_DRM_VENDOR_MIN to ERROR_DRM_VENDOR_MAX are
reflected in the message that is reported to the app, which is
MediaDrmStateException.getDiagnosticInfo().
Many errors map to kErrorCDMGeneric, especially KEY_ERROR is used as a
generic error in CDM. This fix defines more specific error codes in the
CDM for places where KEY_ERROR is returned.
Merge from http://go/wvgerrit/14071
bug: 19244061
Change-Id: I688bf32828f997000fea041dd29567dde18ac677