pkg/http: Removed uses of Chain.track

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 http.utils;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';
 
-import 'package:stack_trace/stack_trace.dart';
-
 import 'byte_stream.dart';
 
 /// Converts a URL query string (or `application/x-www-form-urlencoded` body)
 /// into a [Map] from parameter names to values.
 ///
 ///     queryToMap("foo=bar&baz=bang&qux");
 ///     //=> {"foo": "bar", "baz": "bang", "qux": ""}
 Map<String, String> queryToMap(String queryList, {Encoding encoding}) {
   var map = {};
   for (var pair in queryList.split("&")) {
@@ skipping 166 matching lines @@
   }
 
   int get hashCode => first.hashCode ^ last.hashCode;
 }
 
 /// Configures [future] so that its result (success or exception) is passed on
 /// to [completer].
 void chainToCompleter(Future future, Completer completer) {
   future.then(completer.complete, onError: completer.completeError);
 }
-
-/// Like [Future.sync], but wraps the Future in [Chain.track] as well.
-Future syncFuture(callback()) => Chain.track(new Future.sync(callback));