GenericSource: reset mDrmManagerClient when mDataSource is cleared. am: 224858e719 am: 69c8e36da7 am: 3fcddfd23a
am: e01ba47052

* commit 'e01ba470525155c1c36e53d242a12a778069a5bc':
  GenericSource: reset mDrmManagerClient when mDataSource is cleared.