tYT3z, https://goo.gl/rvnB1g, https://goo.gl/z0URJ0
          var mediaKeys = access.createMediaKeys();
          var persistentState = false;
          try {
            // This will throw if persistent licenses are not supported.
            mediaKeys.createSession('persistent-license');
            persistentState = true;
          } catch (e) {}

          support[keySystem] = {persistentState: persistentState};
        }, function() {
          support[keySystem] = null;
        });
    tests.push(p);
