implement null aware ops, fixes #249

lib/runtime/dart/async.js

 dart_library.library('dart/async', null, /* Imports */[
   "dart_runtime/dart",
   'dart/core',
   'dart/_internal',
   'dart/collection'
 ], /* Lazy imports */[
   'dart/_isolate_helper'
 ], function(exports, dart, core, _internal, collection, _isolate_helper) {
   'use strict';
   let dartx = dart.dartx;
@@ skipping 845 matching lines @@
     }
   }
   let _zone = Symbol('_zone');
   let _state = Symbol('_state');
   let _onData = Symbol('_onData');
   let _onError = Symbol('_onError');
   let _onDone = Symbol('_onDone');
   let _cancelFuture = Symbol('_cancelFuture');
   let _pending = Symbol('_pending');
   let _setPendingEvents = Symbol('_setPendingEvents');
+  let _isCanceled = Symbol('_isCanceled');
   let _extractPending = Symbol('_extractPending');
-  let _isCanceled = Symbol('_isCanceled');
   let _isPaused = Symbol('_isPaused');
   let _isInputPaused = Symbol('_isInputPaused');
   let _inCallback = Symbol('_inCallback');
   let _guardCallback = Symbol('_guardCallback');
   let _onPause = Symbol('_onPause');
   let _decrementPauseCount = Symbol('_decrementPauseCount');
   let _hasPending = Symbol('_hasPending');
   let _mayResumeInput = Symbol('_mayResumeInput');
   let _onResume = Symbol('_onResume');
   let _cancel = Symbol('_cancel');
   let _isClosed = Symbol('_isClosed');
   let _waitsForCancel = Symbol('_waitsForCancel');
   let _canFire = Symbol('_canFire');
   let _cancelOnError = Symbol('_cancelOnError');
   let _onCancel = Symbol('_onCancel');
   let _incrementPauseCount = Symbol('_incrementPauseCount');
   let _sendData = Symbol('_sendData');
   let _addPending = Symbol('_addPending');
   let _sendError = Symbol('_sendError');
+  let _sendDone = Symbol('_sendDone');
   let _close = Symbol('_close');
-  let _sendDone = Symbol('_sendDone');
   let _checkState = Symbol('_checkState');
   let _BufferingStreamSubscription$ = dart.generic(function(T) {
     class _BufferingStreamSubscription extends core.Object {
       _BufferingStreamSubscription(onData, onError, onDone, cancelOnError) {
         this[_zone] = Zone.current;
         this[_state] = dart.notNull(cancelOnError) ? _BufferingStreamSubscription$()._STATE_CANCEL_ON_ERROR : 0;
         this[_onData] = null;
         this[_onError] = null;
         this[_onDone] = null;
         this[_cancelFuture] = null;
@@ skipping 5014 matching lines @@
   exports.ScheduleMicrotaskHandler = ScheduleMicrotaskHandler;
   exports.CreateTimerHandler = CreateTimerHandler;
   exports.CreatePeriodicTimerHandler = CreatePeriodicTimerHandler;
   exports.PrintHandler = PrintHandler;
   exports.ForkHandler = ForkHandler;
   exports.ZoneSpecification = ZoneSpecification;
   exports.ZoneDelegate = ZoneDelegate;
   exports.Zone = Zone;
   exports.runZoned = runZoned;
 });