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

runtime/observatory/tests/service/graph_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
 
 import 'package:observatory/object_graph.dart';
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 
 class Foo {
   Object left;
   Object right;
 }
@@ skipping 68 matching lines @@
   expect(first.successors.length,
          equals(2 + second.successors.length));
   // ... and specifically, that it retains exactly itself + the long one.
   expect(first.retainedSize,
          equals(first.shallowSize + second.shallowSize));
 },
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeBefore: script);