Fix API misuse bug I introduced when fixing another API misuse bug. :-)

utils/pub/io.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.
 
 /**
  * Helper functionality to make working with IO easier.
  */
 #library('io');
 
 #import('dart:io');
@@ skipping 594 matching lines @@
   destination = _getPath(destination);
 
   if (Platform.operatingSystem == "windows") {
     return _extractTarGzWindows(stream, destination);
   }
 
   var process = Process.start("tar",
       ["--extract", "--gunzip", "--directory", destination]);
   var completer = new Completer<int>();
 
+  process.onExit = completer.complete;
+  process.onError = completer.completeException;
+
   // Wait for the process to be fully started before writing to its
   // stdin stream.
   process.onStart = () {
     stream.pipe(process.stdin);
     process.stdout.pipe(stdout, close: false);
     process.stderr.pipe(stderr, close: false);
-
-    process.onExit = completer.complete;
-    process.onError = completer.completeException;
   };
 
   return completer.future.transform((exitCode) => exitCode == 0);
 }
 
 Future<bool> _extractTarGzWindows(InputStream stream, String destination) {
   // Find 7zip.
   var scriptDir = new Path(new Options().script).directoryPath;
 
   // Note: This line of code gets munged by create_sdk.py to be the correct
@@ skipping 72 matching lines @@
   return new Directory(entry);
 }
 
 /**
  * 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 new Uri.fromString(uri);
 }