Clear analyzer warning on Observatory

runtime/observatory/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;
 
 // Some value smaller than the object ring, so requesting a large array
 // doesn't result in an expired ref because the elements lapped it in the
 // object ring.
 const int kDefaultFieldLimit = 100;
@@ skipping 423 matching lines @@
     size = map['size'];
   }
 }
 
 class RetainingObject implements M.RetainingObject {
   int get retainedSize => object.retainedSize;
   final HeapObject object;
   RetainingObject(this.object);
 }
 
-abstract class ServiceObjectOwner extends ServiceObject
-    implements M.ServiceObjectOwner {
+abstract class ServiceObjectOwner extends ServiceObject {
   /// Creates an empty [ServiceObjectOwner].
   ServiceObjectOwner._empty(ServiceObjectOwner owner) : super._empty(owner);
 
   /// Builds a [ServiceObject] corresponding to the [id] from [map].
   /// The result may come from the cache.  The result will not necessarily
   /// be [loaded].
   ServiceObject getFromMap(Map map);
 
   Future<M.Object> invokeRpc(String method, Map params);
 }
@@ skipping 4247 matching lines @@
   final String alias;
   final String method;
   final String service;
 
   Service(this.alias, this.method, this.service) {
     assert(this.alias != null);
     assert(this.method != null);
     assert(this.service != null);
   }
 }