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

runtime/observatory/tests/service/string_escaping_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
 
 library string_escaping_test;
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 
 var ascii;
 var latin1;
 var unicode;
@@ skipping 67 matching lines @@
     expectFullString('nullInTheMiddle', nullInTheMiddle);
     expectTruncatedString('longStringEven', longStringEven);
     expectTruncatedString('longStringOdd', longStringOdd);
     expectFullString('malformedWithLeadSurrogate', malformedWithLeadSurrogate);
     expectFullString('malformedWithTrailSurrogate', malformedWithTrailSurrogate);
   }),
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeBefore: script);