@GwtIncompatible
@ElementTypesAreNonnullByDefault
public abstract class FinalizablePhantomReference<T> extends PhantomReference<T>
    implements FinalizableReference {
  /**
   * Constructs a new finalizable phantom reference.
   *
   * @param referent to phantom reference
   * @param queue that should finalize the referent
   */
  protected FinalizablePhantomReference(@CheckForNull T referent, FinalizableReferenceQueue queue) {