Address observatory analysis issues.

runtime/observatory/tests/service/async_single_step_out_test.dart

Index: runtime/observatory/tests/service/async_single_step_out_test.dart
diff --git a/runtime/observatory/tests/service/async_single_step_out_test.dart b/runtime/observatory/tests/service/async_single_step_out_test.dart
index f66360f1507e727c90e76cf575a2fd063026eccd..6ad5e78c11ebf576f8f9499e59fbfe5f2a78edfd 100644
--- a/runtime/observatory/tests/service/async_single_step_out_test.dart
+++ b/runtime/observatory/tests/service/async_single_step_out_test.dart
@@ -4,17 +4,15 @@
 // 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 = 20;
-const LINE_B = 21;
-const LINE_C = 26;
-const LINE_D = 27;
-const LINE_E = 28;
+const LINE_A = 18;
+const LINE_B = 19;
+const LINE_C = 24;
+const LINE_D = 25;
+const LINE_E = 26;
 
 helper() async {
   print('helper'); // LINE_A.