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

runtime/observatory/tests/service/echo_test.dart

Index: runtime/observatory/tests/service/echo_test.dart
diff --git a/runtime/observatory/tests/service/echo_test.dart b/runtime/observatory/tests/service/echo_test.dart
index 39b365138fe871a94f77358627874b2c9e0931ec..b64b177a6a165db87fa25b8f11169ba16bc5806b 100644
--- a/runtime/observatory/tests/service/echo_test.dart
+++ b/runtime/observatory/tests/service/echo_test.dart
@@ -1,7 +1,7 @@
 // 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 'dart:async';
 import 'package:observatory/service_io.dart';
@@ -35,7 +35,7 @@ var tests = [
     subscription.cancel();
     completer.complete();
   });
-  
+
   await isolate.invokeRpc('_triggerEchoEvent', { 'text': 'hello' });
   await completer.future;
 },