anchor.diff:     * that was requested using the [resumeCapability].
      *
      * When all active pause requests have been cancelled, the isolate
  -   * will continue handling normal messages.
  +   * will continue processing events and handling normal messages.
      *
      * The capability must be one returned by a call to [pause] on this
      * isolate, otherwise the resume call does nothing.
  
positive.code:   /**
     * Requests the isolate to pause.
     *
     * The isolate should stop handling events by pausing its event queue.
     * The request will eventually make the isolate stop doing anything.
     * It will be handled before any other messages that are later sent to the
     * isolate from the current isolate, but no other guarantees are provided.
     *
     * The event loop may be paused before previously sent, but not yet exeuted,
     * messages have been reached.
     *
     * If [resumeCapability] is provided, it is used to identity the pause,
     * and must be used again to end the pause using [resume].
  
negative.code:    * only one resume with that capability is needed to end the pause.
     *
     * If an isolate is paused using more than one capability,
     * each pause must be individually ended before the isolate resumes.
     *
     * Returns the capability that must be used to end the pause.
     */
    Capability pause([Capability resumeCapability]) {
      resumeCapability ??= new Capability();
      _pause(resumeCapability);
      return resumeCapability;
    }
  