Rework error handling in the service protocol and in Observatory.

runtime/observatory/lib/src/elements/heap_map.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 heap_map_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'dart:math';
 import 'observatory_element.dart';
@@ skipping 143 matching lines @@
   void _handleMouseMove(MouseEvent event) {
     var info = _objectAt(event.offset);
     var addressString = '${info.size}B @ 0x${info.address.toRadixString(16)}';
     var className = _classNameAt(event.offset);
     status = (className == '') ? '-' : '$className $addressString';
   }
 
   void _handleClick(MouseEvent event) {
     var address = _objectAt(event.offset).address.toRadixString(16);
     isolate.getObjectByAddress(address).then((result) {
-      if (result is DartError) {
-        Logger.root.severe(result.message);
-      } else if (result.type != 'Sentinel') {
+      if (result.type != 'Sentinel') {
         app.locationManager.go(gotoLink('/inspect', result));
       }
     });
   }
 
   void _updateFragmentationData() {
     if (fragmentation == null || _fragmentationCanvas == null) {
       return;
     }
     _updateClassList(
@@ skipping 50 matching lines @@
       return;
     }
     isolate.invokeRpc('getHeapMap', {}).then((ServiceMap response) {
       assert(response['type'] == 'HeapMap');
       fragmentation = response;
     }).catchError((e, st) {
       Logger.root.info('$e $st');
     });
   }
 
-  void refresh(var done) {
+  Future refresh() {
     if (isolate == null) {
-      return;
+      return new Future.value(null);
     }
-    isolate.invokeRpc('getHeapMap', {}).then((ServiceMap response) {
+    return isolate.invokeRpc('getHeapMap', {}).then((ServiceMap response) {
       assert(response['type'] == 'HeapMap');
       fragmentation = response;
-    }).catchError((e, st) {
-      Logger.root.info('$e $st');
-    }).whenComplete(done);
+    });
   }
 
   void fragmentationChanged(oldValue) {
     // Async, in case attached has not yet run (observed in JS version).
     new Future(() {
       _updateFragmentationData();
     });
   }
 }