Add Iterable.fold (and Stream.fold) which replace `reduce`.

runtime/bin/process_patch.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.
 
 patch class _WindowsCodePageDecoder {
   /* patch */ static String _decodeBytes(List<int> bytes)
       native "SystemEncodingToString";
 }
 
 
@@ skipping 281 matching lines @@
   }
 
   // Start the underlying process.
   return Process.start(path, arguments, options).then((Process p) {
     // Make sure the process stdin is closed.
     p.stdin.close();
 
     // Setup stdout handling.
     Future<StringBuffer> stdout = p.stdout
         .transform(new StringDecoder(stdoutEncoding))
-        .reduce(
+        .fold(
             new StringBuffer(),
             (buf, data) {
               buf.write(data);
               return buf;
             });
 
     Future<StringBuffer> stderr = p.stderr
         .transform(new StringDecoder(stderrEncoding))
-        .reduce(
+        .fold(
             new StringBuffer(),
             (buf, data) {
               buf.write(data);
               return buf;
             });
 
     return Future.wait([p.exitCode, stdout, stderr]).then((result) {
       return new _ProcessResult(result[0],
                                 result[1].toString(),
                                 result[2].toString());
     });
   });
 }
 
 
 class _ProcessResult implements ProcessResult {
   const _ProcessResult(int this.exitCode,
                        String this.stdout,
                        String this.stderr);
 
   final int exitCode;
   final String stdout;
   final String stderr;
 }