anchor.diff:     *     control returns to the event loop of the receiving isolate,
      *     after the current event, and any already scheduled control events,
      *     are completed.
  +   *
  +   * If [terminateCapability] is `null`, or it's not the terminate capability
  +   * of the isolate identified by [controlPort],
  +   * the kill request is ignored by the receiving isolate.
      */
     external void kill({int priority: BEFORE_NEXT_EVENT});
   
  
positive.code:    * anywhere else, so the capabilities should come from the same isolate as
     * the control port.
     *
     * If all the available capabilities are included,
     * there is no reason to create a new object,
     * since the behavior is defined entirely
     * by the control port and capabilities.
     */
    Isolate(this.controlPort, {this.pauseCapability,
                               this.terminateCapability});
  
negative.code:    * event loop and shut down the isolate.
     *
     * This call requires the [terminateCapability] for the isolate.
     * If the capability absent or wrong, no change is made.
     *
     * Since isolates run concurrently, it's possible for it to exit due to an
     * error before errors are set non-fatal.
  