Enable strict flags for all service tests

runtime/observatory/test/contexts_test.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.
+// VMOptions=--compile-all --error_on_bad_type --error_on_bad_override --checked
 
 library inbound_references_test;
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 
 var cleanBlock, copyingBlock, fullBlock, fullBlockWithChain;
 
 Function genCleanBlock() {
@@ skipping 107 matching lines @@
             expect(outerCtxt2.parentContext.isNull, isTrue);
           });
         });
       });
     });
   }),
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeBefore: script);