Use dartfmt on Observatory code

runtime/observatory/lib/src/repositories/instance.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
 
 part of repositories;
 
 class InstanceRepository extends M.InstanceRepository {
   Future<M.Instance> get(M.IsolateRef i, String id,
-                         {int count: S.kDefaultFieldLimit}) async{
+      {int count: S.kDefaultFieldLimit}) async {
     S.Isolate isolate = i as S.Isolate;
     assert(isolate != null);
     assert(count != null);
     return (await isolate.getObject(id, count: count)) as S.Instance;
   }
 }