Make RegExp's constructor non-const.

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:crypto';
 import 'dart:io';
 import 'dart:isolate';
 import 'dart:scalarlist';
@@ skipping 96 matching lines @@
 }
 
 /// Converts [string] into a byte array according to [encoding].
 List<int> encodeString(String string, Encoding encoding) {
   // TODO(nweiz): implement this once issue 6284 is fixed.
   return string.charCodes;
 }
 
 /// A regular expression that matches strings that are composed entirely of
 /// ASCII-compatible characters.
-final RegExp _ASCII_ONLY = const RegExp(r"^[\x00-\x7F]+$");
+final RegExp _ASCII_ONLY = new RegExp(r"^[\x00-\x7F]+$");
 
 /// Returns whether [string] is composed entirely of ASCII-compatible
 /// characters.
 bool isPlainAscii(String string) => _ASCII_ONLY.hasMatch(string);
 
 /// Converts [input] into a [Uint8List]. If [input] is a [ByteArray] or
 /// [ByteArrayViewable], this just returns a view on [input].
 Uint8List toUint8List(List<int> input) {
   if (input is Uint8List) return input;
   if (input is ByteArrayViewable) input = input.asByteArray();
@@ skipping 48 matching lines @@
 /// The return values of all [Future]s are discarded. Any errors will cause the
 /// iteration to stop and will be piped through the return value.
 Future forEachFuture(Iterable input, Future fn(element)) {
   var iterator = input.iterator();
   Future nextElement(_) {
     if (!iterator.hasNext) return new Future.immediate(null);
     return fn(iterator.next()).chain(nextElement);
   }
   return nextElement(null);
 }