Merge from widevine repo of http://go/wvgerrit/21560
For OEMCrypto v12 we explicitly require OEMCrypto_GetRandom to handle
buffers up to 32 bytes long. This CL relaces the use of GetRandom
with openssl's RAND_psuedo_bytes to fill test vectors.
b/31464102
Change-Id: Ia0006b92bb12b98e9c130068dbb31b5f67281de2