Fix --compile_all flag (--compile-all is wrong)

runtime/observatory/tests/service/mirror_references_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
+// VMOptions=--compile_all --error_on_bad_type --error_on_bad_override
 
 library vm_references_test;
 
 import 'dart:mirrors';
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 
 class Foo { }
 
@@ skipping 24 matching lines @@
     expect(ref.referent, isNull);
     var loadedRef = await ref.load();
     expect(loadedRef.referent, isNotNull);
     expect(loadedRef.referent.name, equals('Foo'));
     expect(loadedRef.referent, equals(foo.clazz));
   },
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeBefore: script);