Don't call dinvoke on Object methods

lib/runtime/dart/_isolate_helper.js

 var _isolate_helper;
 (function(exports) {
   'use strict';
   // Function _serializeMessage: (dynamic) → dynamic
   function _serializeMessage(message) {
     return new _Serializer().serialize(message);
   }
   // Function _deserializeMessage: (dynamic) → dynamic
   function _deserializeMessage(message) {
     return new _Deserializer().deserialize(message);
@@ skipping 577 matching lines @@
         if (self.console && self.console.error) {
           self.console.error(error, stackTrace);
         } else {
           core.print(error);
           if (stackTrace != null)
             core.print(stackTrace);
         }
         return;
       }
       let message = new core.List(2);
-      message[core.$set](0, dart.dinvoke(error, 'toString'));
+      message[core.$set](0, error.toString());
       message[core.$set](1, stackTrace == null ? null : stackTrace.toString());
       for (let port of this.errorPorts)
         port.send(message);
     }
     eval(code) {
       let old = exports._globalState.currentContext;
       exports._globalState.currentContext = this;
       this[_setGlobals]();
       let result = null;
       this[_isExecutingEvent] = true;
@@ skipping 766 matching lines @@
   exports.leaveJsAsync = leaveJsAsync;
   exports.isWorker = isWorker;
   exports.startRootIsolate = startRootIsolate;
   exports.IsolateNatives = IsolateNatives;
   exports.RawReceivePortImpl = RawReceivePortImpl;
   exports.ReceivePortImpl = ReceivePortImpl;
   exports.TimerImpl = TimerImpl;
   exports.hasTimer = hasTimer;
   exports.CapabilityImpl = CapabilityImpl;
 })(_isolate_helper || (_isolate_helper = {}));