Address observatory analysis issues.

runtime/observatory/tests/service/async_single_step_into_test.dart

 // Copyright (c) 2017, 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=--error_on_bad_type --error_on_bad_override  --verbose_debug --async_debugger
 
 import 'dart:developer';
-import 'package:observatory/models.dart' as M;
-import 'package:observatory/service_io.dart';
-import 'package:unittest/unittest.dart';
+
 import 'service_test_common.dart';
 import 'test_helper.dart';
 
-const LINE_A = 19;
-const LINE_B = 20;
-const LINE_C = 25;
-const LINE_D = 26;
+const LINE_A = 17;
+const LINE_B = 18;
+const LINE_C = 23;
+const LINE_D = 24;
 
 helper() async {
   print('helper'); // LINE_A.
   print('foobar'); // LINE_B.
 }
 
 testMain() {
   debugger();
   print('mmmmm'); // LINE_C.
   helper(); // LINE_D.
@@ skipping 10 matching lines @@
   hasStoppedAtBreakpoint,
   stoppedAtLine(LINE_A),
   stepOver, // print.
   hasStoppedAtBreakpoint,
   stoppedAtLine(LINE_B),
   resumeIsolate
 ];
 
 main(args) =>
     runIsolateTestsSynchronous(args, tests, testeeConcurrent: testMain);