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

runtime/observatory/tests/service/get_object_rpc_test.dart

 // Copyright (c) 2015, 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 get_object_rpc_test;
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 
 import 'test_helper.dart';
 
 class _DummyClass {
   static var dummyVar = 11;
@@ skipping 436 matching lines @@
       caughtException = true;
       expect(e.code, equals(ServerRpcException.kInvalidParams));
       expect(e.message,
              "getObject: invalid 'objectId' parameter: code/0");
     }
     expect(caughtException, isTrue);
   },
 ];
 
 main(args) async => runIsolateTests(args, tests, testeeBefore:warmup);