Rework error handling in the service protocol and in Observatory.

runtime/observatory/lib/src/elements/isolate_view.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.
 
 library isolate_view_element;
 
 import 'dart:async';
 import 'observatory_element.dart';
 import 'package:observatory/app.dart';
 import 'package:observatory/service.dart';
@@ skipping 103 matching lines @@
     }
   }
 
   void _drawTagProfileChart() {
     var element = shadowRoot.querySelector('#tagProfileChart');
     if (element != null) {
       tagProfileChart.draw(element);
     }
   }
 
-  void refresh(var done) {
-    isolate.reload().whenComplete(done);
+  Future refresh() {
+    return isolate.reload();
   }
 
-  void refreshCoverage(var done) {
-    isolate.refreshCoverage().whenComplete(done);
-  }
-
-  Future pause(_) {
-    return isolate.pause().then((result) {
-        // TODO(turnidge): Instead of asserting here, handle errors
-        // properly.
-        assert(result.type == 'Success');
-        return isolate.reload();
-      });
-  }
-
-  Future resume(_) {
-    return isolate.resume().then((result) {
-        // TODO(turnidge): Instead of asserting here, handle errors
-        // properly.
-        assert(result.type == 'Success');
-        return isolate.reload();
-      });
+  Future refreshCoverage() {
+    return isolate.refreshCoverage();
   }
 }