Use Futures.forEach in http.

pkg/http/lib/src/multipart_request.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 multipart_request;
 
 import 'dart:io';
 import 'dart:math';
 import 'dart:uri';
 import 'dart:utf';
@@ skipping 84 matching lines @@
     void writeUtf8(String string) => stream.write(encodeUtf8(string));
     void writeLine() => stream.write([13, 10]); // \r\n
 
     fields.forEach((name, value) {
       writeAscii('--$boundary\r\n');
       writeAscii(_headerForField(name, value));
       writeUtf8(value);
       writeLine();
     });
 
-    forEachFuture(files, (file) {
+    Futures.forEach(files, (file) {
       writeAscii('--$boundary\r\n');
       writeAscii(_headerForFile(file));
       return writeInputToInput(file.finalize(), stream)
         .transform((_) => writeLine());
     }).then((_) {
       // TODO(nweiz): pass any errors propagated through this future on to
       // the stream. See issue 3657.
       writeAscii('--$boundary--\r\n');
       stream.markEndOfStream();
     });
@@ skipping 41 matching lines @@
   String _boundaryString(int length) {
     var prefix = "dart-http-boundary-";
     var list = new List<int>(length - prefix.length);
     for (var i = 0; i < list.length; i++) {
       list[i] = _BOUNDARY_CHARACTERS[
           _random.nextInt(_BOUNDARY_CHARACTERS.length)];
     }
     return "$prefix${new String.fromCharCodes(list)}";
   }
 }