Merge from Widevine repo of http://go/wvgerrit/95945
The reference oemcrypto and testbed still use old style pointers, even
though we now require a more modern C++ compiler. Updated a few places
where smart pointer would be appropriate.
Bug: 141393616
Test: Ran unit tests
Change-Id: I8b1e155bce241075928e373478d6f8e1001233f9