Display an informative message when we hit the JSON decode bug.

runtime/bin/vmservice/client/lib/src/service/object.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.
 
 part of service;
 
 /// A [ServiceObject] is an object known to the VM service and is tied
 /// to an owning [Isolate].
 abstract class ServiceObject extends Observable {
   /// The owner of this [ServiceObject].  This can be an [Isolate], a
@@ skipping 266 matching lines @@
     // Cache miss.  Get the object from the vm directly.
     return getAsMap(id).then((ObservableMap map) {
         var obj = new ServiceObject._fromMap(this, map);
         if (obj.canCache) {
           _cache.putIfAbsent(id, () => obj);
         }
         return obj;
       });
   }
 
+  Future<ObservableMap> _processMap(ObservableMap map) {
+    // Verify that the top level response is a service map.
+    if (!_isServiceMap(map)) {
+      return new Future.error(
+            new ServiceObject._fromMap(this, toObservable({
+        'type': 'ServiceException',
+        'id': '',
+        'kind': 'FormatException',
+        'response': map,
+        'message': 'Top level service responses must be service maps.',
+      })));
+    }
+    // Preemptively capture ServiceError and ServiceExceptions.
+    if (map['type'] == 'ServiceError') {
+      return new Future.error(new ServiceObject._fromMap(this, map));
+    } else if (map['type'] == 'ServiceException') {
+      return new Future.error(new ServiceObject._fromMap(this, map));
+    }
+    // map is now guaranteed to be a non-error/exception ServiceObject.
+    return new Future.value(map);
+  }
+
   /// Gets [id] as an [ObservableMap] from the service directly. If
   /// an error occurs, the future is completed as an error with a
   /// ServiceError or ServiceException. Therefore any chained then() calls
   /// will only receive a map encoding a valid ServiceObject.
   Future<ObservableMap> getAsMap(String id) {
     return getString(id).then((response) {
       try {
         var map = toObservable(JSON.decode(response));
-        // Verify that the top level response is a service map.
-        if (!_isServiceMap(map)) {
-          return new Future.error(
-                new ServiceObject._fromMap(this, toObservable({
-            'type': 'ServiceException',
-            'id': '',
-            'kind': 'FormatException',
-            'response': map,
-            'message': 'Top level service responses must be service maps.',
-          })));
-        }
-        // Preemptively capture ServiceError and ServiceExceptions.
-        if (map['type'] == 'ServiceError') {
-          return new Future.error(new ServiceObject._fromMap(this, map));
-        } else if (map['type'] == 'ServiceException') {
-          return new Future.error(new ServiceObject._fromMap(this, map));
-        }
-        // map is now guaranteed to be a non-error/exception ServiceObject.
-        return map;
+        return _processMap(map);
       } catch (e, st) {
-        print(e);
-        print(st);
+        // Two decode failures.

[turnidge, 2014/05/06 18:44:22]

remove comment.

         return new Future.error(
               new ServiceObject._fromMap(this, toObservable({
           'type': 'ServiceException',
           'id': '',
           'kind': 'DecodeException',
-          'response': response,
+          'response':
+              'This is likely a result of a known V8 bug. Although the '
+              'the bug has been fixed the fix may not be in your Chrome'
+              ' version. For more information see dartbug.com/18385. '
+              'Observatory is still functioning and you should try your'
+              ' action again.',
           'message': 'Could not decode JSON: $e',
         })));
       }
     }).catchError((error) {
       // ServiceError, forward to VM's ServiceError stream.
       errors.add(error);
       return new Future.error(error);
     }, test: (e) => e is ServiceError).catchError((exception) {
       // ServiceException, forward to VM's ServiceException stream.
       exceptions.add(exception);
@@ skipping 1143 matching lines @@
     var v = list[i];
     if ((v is ObservableMap) && _isServiceMap(v)) {
       list[i] = owner.getFromMap(v);
     } else if (v is ObservableList) {
       _upgradeObservableList(v, owner);
     } else if (v is ObservableMap) {
       _upgradeObservableMap(v, owner);
     }
   }
 }