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

runtime/observatory/tests/service/steal_breakpoint_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 --steal-breakpoints
+// VMOptions=--compile_all --error_on_bad_type --error_on_bad_override --steal-breakpoints
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 import 'dart:async';
 
 int counter = 0;
 
 void periodicTask(_) {
   counter++;  // Line 14.  We set our breakpoint here.
@@ skipping 56 matching lines @@
       completer.complete();
     }
   });
   isolate.resume();
   await completer.future;
 },
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeBefore: startTimer);