Big merge from experimental to bleeding edge.

pkg/http/lib/src/multipart_file.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_file;
 
 import 'dart:io';
 
 import 'utils.dart';
 
@@ skipping 67 matching lines @@
 
   // TODO(nweiz): Infer the content-type from the filename.
   /// Creates a new [MultipartFile] from a [File].
   ///
   /// [filename] defaults to the name of the file on disk. [contentType]
   /// currently defaults to `application/octet-stream`, but in the future may be
   /// inferred from [filename].
   static Future<MultipartFile> fromFile(String field, File file,
       {String filename, ContentType contentType}) {
     if (filename == null) filename = new Path(file.name).filename;
-    return file.length().transform((length) {
+    return file.length().then((length) {
       return new MultipartFile(field, file.openInputStream(), length,
           filename: filename,
           contentType: contentType);
     });
   }
 
   // Finalizes the file in preparation for it being sent as part of a
   // [MultipartRequest]. This returns an [InputStream] that should emit the body
   // of the file. The stream may be closed to indicate an empty file.
   InputStream finalize() {
     if (isFinalized) {
       throw new StateError("Can't finalize a finalized MultipartFile.");
     }
     _isFinalized = true;
     return _stream;
   }
 }