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

runtime/observatory/tests/service/weak_properties_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 { }
 class Bar { }
@@ skipping 42 matching lines @@
     // we expect.
     expect(loadedProp.key, isNotNull);
     expect(loadedProp.key.clazz, equals(key.clazz));
     expect(loadedProp.value, isNotNull);
     expect(loadedProp.value.clazz, equals(value.clazz));
   },
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeBefore: script);