Add isolate tag-profile and better handling of errors

runtime/bin/vmservice/client/lib/src/app/application.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of app;
 
 /// A request response interceptor is called for each response.
 typedef void RequestResponseInterceptor();
 
 /// The observatory application. Instances of this are created and owned
 /// by the observatory_application custom element.
 class ObservatoryApplication extends Observable {
   @observable final LocationManager locationManager;
   @observable final VM vm;
   @observable Isolate isolate;
 
   /// The current [ServiceObject] being viewed by the application.
   @observable ServiceObject response;
 
   /// Any client-level arguments for viewing the current response.
   @observable String args;
   // TODO(turnidge): Make args a Map.
 
   void _initOnce() {
     // Only called once.
     assert(locationManager._app == null);
     locationManager._app = this;
     locationManager.init();
+    vm.errors.stream.listen(_onError);
+    vm.exceptions.stream.listen(_onException);
+  }
+
+  void _onError(ServiceError error) {
+    response = error;
+    // No id, clear the hash.
+    locationManager.clearCurrentHash();
+  }
+
+  void _onException(ServiceException exception) {
+    response = exception;
+    // No id, clear the hash.
+    locationManager.clearCurrentHash();
   }
 
   ObservatoryApplication.devtools() :
       locationManager = new LocationManager(),
       vm = new DartiumVM() {
     _initOnce();
   }
 
   ObservatoryApplication() :
       locationManager = new LocationManager(),
       vm = new HttpVM() {
     _initOnce();
   }
 }