Function when

tools/ngui/static/js/lib/angular.js:6951–6986

(value, callback, errback)

   * @returns {Promise} Returns a promise of the passed value or promise
   */
  var when = function(value, callback, errback) {
    var result = defer(),
        done;

    var wrappedCallback = function(value) {
      try {
        return (callback || defaultCallback)(value);
      } catch (e) {
        exceptionHandler(e);
        return reject(e);
      }
    };

    var wrappedErrback = function(reason) {
      try {
        return (errback || defaultErrback)(reason);
      } catch (e) {
        exceptionHandler(e);
        return reject(e);
      }
    };

    nextTick(function() {
      ref(value).then(function(value) {
        if (done) return;
        done = true;
        result.resolve(ref(value).then(wrappedCallback, wrappedErrback));
      }, function(reason) {
        if (done) return;
        done = true;
        result.resolve(wrappedErrback(reason));
      });
    });

    return result.promise;
  };


  function defaultCallback(value) {