Merge IO v2 branch to bleeding edge

samples/buildhook2/build.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.
 
 import "dart:io";
 import "package:args/args.dart";
 
 bool cleanBuild;
 bool fullBuild;
 bool useMachineInterface;
@@ skipping 52 matching lines @@
 
   cleanBuild = args["clean"];
   fullBuild = args["full"];
 }
 
 /**
  * Delete all generated files.
  */
 void handleCleanCommand() {
   Directory current = new Directory.current();
-  current.list(recursive: true).onFile = _maybeClean;
+  current.list(recursive: true).listen((entity) {
+    if (entity.isFile) _maybeClean(entity.path)
+  });
 }
 
 /**
  * Recursively scan the current directory looking for .foo files to process.
  */
 void handleFullBuild() {
   var files = <String>[];
-  var lister = new Directory.current().list(recursive: true);
-
-  lister.onFile = (file) => files.add(file);
-  lister.onDone = (_) => handleChangedFiles(files);
+  new Directory.current().list(recursive: true).listen(
+      (entity) {
+        if (entity.isFile) files.add(entity.path);
+      },
+      onDone: () => handleChangedFiles(files));
 }
 
 /**
  * Process the given list of changed files.
  */
 void handleChangedFiles(List<String> files) {
   files.forEach(_processFile);
 }
 
 /**
  * Process the given list of removed files.
  */
 void handleRemovedFiles(List<String> files) {
 
 }
 
 /**
  * Convert a .foo file to a .foobar file.
  */
 void _processFile(String arg) {
   if (arg.endsWith(".foo")) {
     print("processing: ${arg}");
 
     File file = new File(arg);
 
     String contents = file.readAsStringSync();
 
     File outFile = new File("${arg}bar");
 
-    OutputStream out = outFile.openOutputStream();
-    out.writeString("// processed from ${file.name}:\n");
+    var out = outFile.openWrite();
+    out.addString("// processed from ${file.name}:\n");
     if (contents != null) {
-      out.writeString(contents);
+      out.addString(contents);
     }
     out.close();
 
     _findErrors(arg);
 
     print("wrote: ${outFile.name}");
   }
 }
 
 void _findErrors(String arg) {
@@ skipping 13 matching lines @@
 }
 
 /**
  * If this file is a generated file (based on the extension), delete it.
  */
 void _maybeClean(String file) {
   if (file.endsWith(".foobar")) {
     new File(file).delete();
   }
 }