throw newAssertionError("Unexpected fallback", t);
      }
    };
  }

  /** Alternative to AssertionError(String, Throwable), which doesn't exist in GWT 2.6.1. */
  private static AssertionError newAssertionError(String message, Throwable cause) {
    AssertionError e = new AssertionError(message);
    e.initCause(cause);
    return e;
  }

  // catchingAsync tests cloned from the old withFallback tests:

        if (!removeEntry(e, e.getHash(), RemovalCause.EXPIRED)) {
          throw new AssertionError();
        }
      }
      while ((e = accessQueue.peek()) != null && map.isExpired(e, now)) {
        if (!removeEntry(e, e.getHash(), RemovalCause.EXPIRED)) {
          throw new AssertionError();
        }
      }
    }

    // eviction

    @GuardedBy("this")

        throw newAssertionError("Unexpected fallback", t);
      }
    };
  }

  /** Alternative to AssertionError(String, Throwable), which doesn't exist in GWT 2.6.1. */
  private static AssertionError newAssertionError(String message, Throwable cause) {
    AssertionError e = new AssertionError(message);
    e.initCause(cause);
    return e;
  }

  // catchingAsync tests cloned from the old withFallback tests:

        if (!removeEntry(e, e.getHash(), RemovalCause.EXPIRED)) {
          throw new AssertionError();
        }
      }
      while ((e = accessQueue.peek()) != null && map.isExpired(e, now)) {
        if (!removeEntry(e, e.getHash(), RemovalCause.EXPIRED)) {
          throw new AssertionError();
        }
      }
    }

    // eviction

    @GuardedBy("this")

        case WILL_CLOSE:
        case CLOSING:
        case CLOSED:
          throw new IllegalStateException("Cannot call finishToFuture() twice");

        case OPEN:
          throw new AssertionError();
      }
    }
    return future;
  }

  /**
   * Marks this step as the last step in the {@code ClosingFuture} pipeline. When this step is done,