Change dart:io to use Future for one-shot operations.

utils/compiler/build_helper.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('dart:uri');
 
 #import('../../lib/compiler/implementation/util/uri_extras.dart');
 #import('../../lib/compiler/implementation/filenames.dart');
 
@@ skipping 33 matching lines @@
 
   f = new File('${uriPathToNative(uri.path)}.bat');
   stream = f.openSync(FileMode.WRITE);
   try {
     stream.writeStringSync(batFile);
   } finally {
     stream.closeSync();
   }
 
   if (Platform.operatingSystem != 'windows') {
-    onExit(int exitCode, String stdout, String stderr) {
-      if (exitCode != 0) {
-        print(stdout);
-        print(stderr);
-        exit(exitCode);
+    onExit(ProcessResult result) {
+      if (result.exitCode != 0) {
+        print(result.stdout);
+        print(result.stderr);
+        exit(result.exitCode);
       }
     }
-    new Process.run('/bin/chmod', ['+x', uri.path], null, onExit);
+    Process.run('/bin/chmod', ['+x', uri.path]).then(onExit);
   }
 }
 
 List<String> buildScript(Uri dartUri, Uri dartVmLocation, String options) {
   Uri dart2jsUri = dartUri.resolve('lib/compiler/implementation/dart2js.dart');
   String dart2jsPath = relativize(dartVmLocation, dart2jsUri);
   String dart2jsPathWin = dart2jsPath.replaceAll("/", "\\");
 
   print('dartUri = $dartUri');
   print('dartVmLocation = $dartVmLocation');
@@ skipping 20 matching lines @@
 set SCRIPTPATH=%~dp0
 
 REM Does the path have a trailing slash? If so, remove it.
 if %SCRIPTPATH:~-1%==\ set SCRIPTPATH=%SCRIPTPATH:~0,-1%
 
 set arguments=%*
 
 "%SCRIPTPATH%\dart.exe"$options "%SCRIPTPATH%$dart2jsPathWin" %arguments%
 '''.replaceAll('\n', '\r\n')];
 }