Fix analyzer errors and warnings for pkg/http.

pkg/http/test/utils.dart

 // Copyright (c) 2012, 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.
 
-library utils;
+library test_utils;
 
 import 'dart:io';
 import 'dart:json';
 import 'dart:uri';
 
 import '../../unittest/lib/unittest.dart';
 import '../lib/http.dart' as http;
 import '../lib/src/utils.dart';
 
 /// The current server instance.
@@ skipping 149 matching lines @@
 const Matcher throwsRedirectLimitExceededException =
     const Throws(isRedirectLimitExceededException);
 
 class _RedirectLimitExceededException extends TypeMatcher {
   const _RedirectLimitExceededException() :
       super("RedirectLimitExceededException");
 
   bool matches(item, MatchState matchState) =>
     item is RedirectLimitExceededException;
 }