Function when

test/angular/1.2/angular.js:11902–11948

(value, callback, errback, progressback)

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

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

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

    var wrappedProgressback = function(progress) {
      try {
        return (isFunction(progressback) ? progressback : defaultCallback)(progress);
      } catch (e) {
        exceptionHandler(e);
      }
    };

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

    return result.promise;
  };


  function defaultCallback(value) {