Removed const from classes arrays in Observatory

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

 // Copyright (c) 2016, 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.
 
 import 'dart:html';
 import 'dart:async';
 import 'package:observatory/models.dart' as M;
 import 'package:observatory/src/elements/curly_block.dart';
 import 'package:observatory/src/elements/instance_ref.dart';
 import 'package:observatory/src/elements/helpers/any_ref.dart';
@@ skipping 102 matching lines @@
       );
     }
 
     content.addAll([
       anyRef(_isolate, reference.source, _instances, queue: _r.queue),
       new SpanElement()..text = ' referenced by ',
       new InboundReferencesElement(_isolate, reference.source, _references,
                                    _instances, queue: _r.queue )
     ]);
 
-    return new DivElement()..classes = ['indent']..children = content;
+    return new DivElement()..classes = ['indent']
+             ..children = content;
   }
 }