Fix a couple of warnings.

sdk/lib/_internal/pub/test/test_pub.dart

 // Copyright (c) 2013, 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.
 
 /// Test infrastructure for testing pub. Unlike typical unit tests, most pub
 /// tests are integration tests that stage some stuff on the file system, run
 /// pub, and then validate the results. This library provides an API to build
 /// tests like that.
 library test_pub;
 
@@ skipping 86 matching lines @@
 
   schedule(() {
     return _closeServer().then((_) {
       return SafeHttpServer.bind("localhost", 0).then((server) {
         _server = server;
         server.listen((request) {
           currentSchedule.heartbeat();
           var response = request.response;
           try {
             var path = request.uri.path.replaceFirst("/", "");
-
-            if (_requestedPaths == null) _requestedPaths = <String>[];
             _requestedPaths.add(path);
 
             response.persistentConnection = false;
             var stream = baseDir.load(path);
 
             new ByteStream(stream).toBytes().then((data) {
               currentSchedule.heartbeat();
               response.statusCode = 200;
               response.contentLength = data.length;
               response.add(data);
@@ skipping 563 matching lines @@
   bool matches(item, MatchState matchState) {
     if (item is! Pair) return false;
     return _firstMatcher.matches(item.first, matchState) &&
         _lastMatcher.matches(item.last, matchState);
   }
 
   Description describe(Description description) {
     description.addAll("(", ", ", ")", [_firstMatcher, _lastMatcher]);
   }
 }