Remove deprecated Strings class.

pkg/http/lib/src/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;
 
 import 'dart:async';
 import 'dart:crypto';
 import 'dart:io';
 import 'dart:scalarlist';
@@ skipping 20 matching lines @@
 }
 
 /// Converts a [Map] from parameter names to values to a URL query string.
 ///
 ///     mapToQuery({"foo": "bar", "baz": "bang"});
 ///     //=> "foo=bar&baz=bang"
 String mapToQuery(Map<String, String> map) {
   var pairs = <List<String>>[];
   map.forEach((key, value) =>
       pairs.add([encodeUriComponent(key), encodeUriComponent(value)]));
-  return Strings.join(pairs.map((pair) => "${pair[0]}=${pair[1]}"), "&");
+  return pairs.map((pair) => "${pair[0]}=${pair[1]}").join("&");
 }
 
 /// Adds all key/value pairs from [source] to [destination], overwriting any
 /// pre-existing values.
 ///
 ///     var a = {"foo": "bar", "baz": "bang"};
 ///     mapAddAll(a, {"baz": "zap", "qux": "quux"});
 ///     a; //=> {"foo": "bar", "baz": "zap", "qux": "quux"}
 void mapAddAll(Map destination, Map source) =>
   source.forEach((key, value) => destination[key] = value);
@@ skipping 263 matching lines @@
 /// [StreamController]. This exists to work around issue 8310.
 Stream wrapStream(Stream stream) {
   var controller = stream.isBroadcast
       ? new StreamController.broadcast()
       : new StreamController();
   stream.listen(controller.add,
       onError: (e) => controller.signalError(e),
       onDone: controller.close);
   return controller.stream;
 }