Address additional analysis issues in the observatory codebase.

runtime/observatory/tests/service/async_single_step_into_test.dart

Index: runtime/observatory/tests/service/async_single_step_into_test.dart
diff --git a/runtime/observatory/tests/service/async_single_step_into_test.dart b/runtime/observatory/tests/service/async_single_step_into_test.dart
index 129ff6a0fc4b5a57d763e49fbb28ce59d4e4f9d2..d4661b44ffc8f02fc6853bda1b6a666923ae4559 100644
--- a/runtime/observatory/tests/service/async_single_step_into_test.dart
+++ b/runtime/observatory/tests/service/async_single_step_into_test.dart
@@ -4,17 +4,11 @@
 // 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 'dart:io';
+
 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;
-
 helper() async {
   print('helper'); // LINE_A.
   print('foobar'); // LINE_B.
@@ -27,18 +21,20 @@ testMain() {
   print('z');
 }
 
+final ScriptLineParser lineParser = new ScriptLineParser(Platform.script);
+
 var tests = [
   hasStoppedAtBreakpoint,
-  stoppedAtLine(LINE_C),
+  stoppedAtLine(lineParser.lineFor('LINE_C')),
   stepOver, // print.
   hasStoppedAtBreakpoint,
-  stoppedAtLine(LINE_D),
+  stoppedAtLine(lineParser.lineFor('LINE_D')),
   stepInto,
   hasStoppedAtBreakpoint,
-  stoppedAtLine(LINE_A),
+  stoppedAtLine(lineParser.lineFor('LINE_A')),
   stepOver, // print.
   hasStoppedAtBreakpoint,
-  stoppedAtLine(LINE_B),
+  stoppedAtLine(lineParser.lineFor('LINE_B')),
   resumeIsolate
 ];