Don't delay IOSink.close() with no subscription to the next instance.

utils/pub/io.dart

 // Copyright (c) 2013, 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.
 
 /// Helper functionality to make working with IO easier.
 library io;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
@@ skipping 266 matching lines @@
   }
 
   return path.normalize(path.join(utilDir, 'pub', target));
 }
 
 // TODO(nweiz): add a ByteSink wrapper to make writing strings to stdout/stderr
 // nicer.
 
 /// A sink that writes to standard output. Errors piped to this stream will be
 /// surfaced to the top-level error handler.
-final EventSink<List<int>> stdoutSink = stdout;
+// TODO: Unrequired wrapper, stdout is now an EventSink<List<int>>.
+final EventSink<List<int>> stdoutSink = _wrapStdio(stdout, "stdout");
 
 /// A sink that writes to standard error. Errors piped to this stream will be
 /// surfaced to the top-level error handler.
-final EventSink<List<int>> stderrSink = stderr;
+// TODO: Unrequired wrapper, stdout is now an EventSink<List<int>>.
+final EventSink<List<int>> stderrSink = _wrapStdio(stderr, "stderr");
 
 /// Wrap the standard output or error [stream] in a [EventSink]. Any errors are
 /// logged, and then the program is terminated. [name] is used for debugging.
 EventSink<List<int>> _wrapStdio(IOSink sink, String name) {
   var pair = consumerToSink(sink);
   pair.last.catchError((e) {
     // This log may or may not work, depending on how the stream failed. Not
     // much we can do about that.
     log.error("Error writing to $name: $e");
     exit(exit_codes.IO);
@@ skipping 427 matching lines @@
   const PubProcessResult(this.stdout, this.stderr, this.exitCode);
 
   bool get success => exitCode == 0;
 }
 
 /// Gets a [Uri] for [uri], which can either already be one, or be a [String].
 Uri _getUri(uri) {
   if (uri is Uri) return uri;
   return Uri.parse(uri);
 }