Fix analyzer warnings in a test.

runtime/observatory/tests/service/regress_28980_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.
 
 import 'dart:async';
 import 'test_helper.dart';
 import 'service_test_common.dart';
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 
@@ skipping 20 matching lines @@
   assert(_lock == null);
   _lock = foo(flutterRoot, 'bin', 'cache', 'lockfile');
   bool locked = false;
   bool printed = false;
   while (!locked) {
     try {
       await _lock.lock();
       locked = true; // LINE_B
     } on FileSystemException {
       if (!printed) {
-        printTrace('Print path: ${_lock.path}');
-        printStatus('Just another line...');
+        print('Print path: ${_lock.path}');
+        print('Just another line...');
         printed = true;
       }
       await new Future<Null>.delayed(const Duration(milliseconds: 50));
     }
   }
 }
 
 Future<Isolate> stepThroughProgram(Isolate isolate) async {
   Completer completer = new Completer();
   int pauseEventsSeen = 0;
@@ skipping 26 matching lines @@
   resumeIsolate,
   hasStoppedAtBreakpoint,
   stepInto,
   stepInto,
   stepInto,
   resumeIsolate,
 ];
 
 main(args) => runIsolateTestsSynchronous(args, tests,
     testeeConcurrent: test_code, pause_on_start: true, pause_on_exit: false);