anchor.diff:     * Called at the beginning of each VM turn in which inner zone code runs.
      * "At the beginning" means before any of the microtasks from the private
      * microtask queue of the inner zone is executed. Notes
  +   *
      * - [onTurnStart] runs repeatedly until no more microstasks are scheduled
      *   within [onTurnStart], [run] or [onTurnDone]. You usually don't want it to
      *   schedule any.  For example, if its first line of code is `new Future.value()`,
  
positive.code:    * Called with any errors from the inner zone.
     */
    ZoneOnError onError;
  
    /// Prevent silently ignoring uncaught exceptions by forwarding such exceptions to the outer zone.
    void _defaultOnError(dynamic e, dynamic s, LongStackTrace ls) =>
        _outerZone.handleUncaughtError(e, s);
  
  
negative.code: part of angular.core_internal;
  
  /**
   * Handles a [VmTurnZone] onTurnDone event.
   */
  typedef void ZoneOnTurnDone();
  
  /**
   * Handles a [VmTurnZone] onTurnDone event.
   */
  typedef void ZoneOnTurnStart();
  
  /**
   * Handles a [VmTurnZone] onError event.
   */
  typedef void ZoneOnError(dynamic error, dynamic stacktrace,
                           LongStackTrace longStacktrace);
  