Merge from widevine side of http://go/wvgerrit/14462
This cleans up some tests in oemcrypto_test.cpp so that they use
vectors instead of arrays. The two reasons this is needed are that
arrays are more likely to use up stack space, and that arrays on the
stack are not initialized.
The lack of initialization caused some negative tests to fail because
buffers that were reused from unencrypted data still contained values
that the test expected not to be there.
Change-Id: Ic1705b6bc581084a9fe3cd573adf34d8219a1a45
9dfa85ae2a