anchor.diff:  part of angular.core_internal;
   
   /**
  - * Handles an [VmTurnZone] onTurnDone event.
  + * Handles a [VmTurnZone] onTurnDone event.
    */
   typedef void ZoneOnTurnDone();
   
   /**
  - * Handles an [VmTurnZone] onTurnDone event.
  + * Handles a [VmTurnZone] onTurnDone event.
    */
   typedef void ZoneOnTurnStart();
   
   /**
  - * Handles an [VmTurnZone] onError event.
  + * Handles a [VmTurnZone] onError event.
    */
   typedef void ZoneOnError(dynamic error, dynamic stacktrace,
                            LongStackTrace longStacktrace);
  
positive.code:   ZoneOnTurnStart onTurnStart;
    void _defaultOnTurnStart() => null;
  
  
    /**
     * Called at the end of each VM turn in which inner zone code runs.
     * "At the end" means after the private microtask queue of the inner zone is
     * exhausted but before the next VM turn.  Notes
     * - This won't wait for microtasks scheduled in zones other than the inner
     *   zone, e.g. those scheduled with [runOutsideAngular].
     * - [onTurnDone] runs repeatedly until no more tasks are scheduled within
  
negative.code:   /**
     * Associates with this
     *
     * - an "outer" [Zone], which is the one that created this.
     * - an "inner" [Zone], which is a child of the outer [Zone].
     *
     * Defaults [onError] to forward errors to the outer [Zone].
     * Defaults [onTurnStart] and [onTurnDone] to no-op functions.
     */
    VmTurnZone() {
      _outerZone = async.Zone.current;
  