Remove --compile_all from all but one service test

runtime/observatory/tests/service/async_continuation_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 --verbose-debug
+// VMOptions=--error_on_bad_type --error_on_bad_override --verbose-debug
 
 import 'dart:async';
 import 'dart:developer';
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 
 foo() {}
 
 doSync() {
@@ skipping 71 matching lines @@
       }
     }
   });
 
   await bp1_hit.future;
   await bp2_hit.future;
   await bp3_hit.future;
 }
 
 main(args) => runIsolateTests(args, [test], testeeConcurrent: testeeDo);