Merge from Widevine repo of http://go/wvgerrit/23581
This CL adds some unit tests to oemcrypto to verify that DecryptCENC
and the generic encrypt and decrypt functions behave correctly when
the input and output buffer is the same. i.e. decrypt in place.
The mock and haystack are also updated to pass the tests.
b/34080119
Change-Id: Ie295bdaddbb8058bebb36f6dab092d307f249ecd