Make stdout/stderr async

sdk/lib/io/stdio.dart

Index: sdk/lib/io/stdio.dart
diff --git a/sdk/lib/io/stdio.dart b/sdk/lib/io/stdio.dart
index f36dd833366e0a982550bf2e7f55beeaed4ddcff..e4bdf01ff05c7bb0b6d68ba8c53d1a743d319d0c 100644
--- a/sdk/lib/io/stdio.dart
+++ b/sdk/lib/io/stdio.dart
@@ -191,36 +191,6 @@ class StdoutException implements IOException {
 }
 
 
-class _StdConsumer implements StreamConsumer<List<int>> {
-  final _file;
-
-  _StdConsumer(int fd) : _file = _File._openStdioSync(fd);
-
-  Future addStream(Stream<List<int>> stream) {
-    var completer = new Completer();
-    var sub;
-    sub = stream.listen(
-        (data) {
-          try {
-            _file.writeFromSync(data);
-          } catch (e, s) {
-            sub.cancel();
-            completer.completeError(e, s);
-          }
-        },
-        onError: completer.completeError,
-        onDone: completer.complete,
-        cancelOnError: true);
-    return completer.future;
-  }
-
-  Future close() {
-    _file.closeSync();
-    return new Future.value();
-  }
-}
-
-
 class _StdSink implements IOSink {
   final IOSink _sink;