Rework error handling in the service protocol and in Observatory.

runtime/observatory/lib/src/elements/isolate_reconnect.dart

 // Copyright (c) 2014, 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.
 
 library isolate_reconnect_element;
 
-import 'dart:html';
 import 'package:polymer/polymer.dart';
 import 'observatory_element.dart';
-import 'package:observatory/app.dart';
-import 'package:observatory/service_html.dart';
 
 @CustomTag('isolate-reconnect')
 class IsolateReconnectElement extends ObservatoryElement {
   IsolateReconnectElement.created() : super.created();
 
   get missingIsolateId {
     return app.locationManager.uri.queryParameters['originalIsolateId'];
   }
 
   linkToContinueIn(isolate) {
     var parameters = new Map.from(app.locationManager.uri.queryParameters);
     parameters['isolateId'] = isolate.id;
     parameters.remove('originalIsolateId');
     var path = parameters.remove('originalPath');
     path = "/$path";
     var generatedUri = new Uri(path: path, queryParameters: parameters);
     return app.locationManager.makeLink(generatedUri.toString());
   }
 }