restore arrow function bind this workaround

lib/runtime/dart/isolate.js

 dart_library.library('dart/isolate', null, /* Imports */[
   "dart_runtime/dart",
   'dart/core',
   'dart/async'
 ], /* Lazy imports */[
   'dart/_isolate_helper'
 ], function(exports, dart, core, async, _isolate_helper) {
   'use strict';
   let dartx = dart.dartx;
   class Capability extends core.Object {
@@ skipping 129 matching lines @@
     get errors() {
       let controller = null;
       let port = null;
       function handleError(message) {
         let errorDescription = dart.as(dart.dindex(message, 0), core.String);
         let stackDescription = dart.as(dart.dindex(message, 1), core.String);
         let error = new RemoteError(errorDescription, stackDescription);
         controller.addError(error, error.stackTrace);
       }
       dart.fn(handleError, dart.void, [dart.dynamic]);
-      controller = async.StreamController.broadcast({sync: true, onListen: dart.fn(() => {
+      controller = async.StreamController.broadcast({sync: true, onListen: dart.fn((() => {
           port = RawReceivePort.new(handleError);
           this.addErrorListener(port.sendPort);
-        }), onCancel: dart.fn(() => {
+        }).bind(this)), onCancel: dart.fn((() => {
           this.removeErrorListener(port.sendPort);
           port.close();
           port = null;
-        })});
+        }).bind(this))});
       return controller.stream;
     }
   }
   dart.setSignature(Isolate, {
     constructors: () => ({Isolate: [Isolate, [SendPort], {pauseCapability: Capability, terminateCapability: Capability}]}),
     methods: () => ({
       pause: [Capability, [], [Capability]],
       [_pause]: [dart.void, [Capability]],
       resume: [dart.void, [Capability]],
       addOnExitListener: [dart.void, [SendPort]],
@@ skipping 88 matching lines @@
   });
   // Exports:
   exports.Capability = Capability;
   exports.IsolateSpawnException = IsolateSpawnException;
   exports.Isolate = Isolate;
   exports.SendPort = SendPort;
   exports.ReceivePort = ReceivePort;
   exports.RawReceivePort = RawReceivePort;
   exports.RemoteError = RemoteError;
 });