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

runtime/observatory/tests/service/evaluate_activation_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
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 
 import 'dart:math' as math;
 
 breakHere() {}
 
 use(dynamic v) => v;
@@ skipping 245 matching lines @@
 }
 
 var tests = [
   testMethod,
   testMethod2,
   testMethod3,
   testMethod4,
 ];
 
 main(args) => runIsolateTests(args, tests);