fixes #157, renaming local library identifiers if needed.

lib/runtime/dart/async.js

Index: lib/runtime/dart/async.js
diff --git a/lib/runtime/dart/async.js b/lib/runtime/dart/async.js
index d7d684f2610a953f2ba4bc1f0b29d7e2e5cadf2d..14098d6c078db7322741ce44129c48afb6438b5c 100644
--- a/lib/runtime/dart/async.js
+++ b/lib/runtime/dart/async.js
@@ -1,5 +1,5 @@
-var async;
-(function(exports) {
+var async, core, _internal, _js_helper, _isolate_helper, collection;
+(function(exports, core, _internal, _js_helper, _isolate_helper, collection) {
   'use strict';
   // Function _invokeErrorHandler: (Function, Object, StackTrace) → dynamic
   function _invokeErrorHandler(errorHandler, error, stackTrace) {
@@ -5366,4 +5366,4 @@ var async;
   exports.ZoneDelegate = ZoneDelegate;
   exports.Zone = Zone;
   exports.runZoned = runZoned;
-})(async || (async = {}));
+})(async || (async = {}), core, _internal, _js_helper || (_js_helper = {}), _isolate_helper || (_isolate_helper = {}), collection);