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

tests/standalone/io/process_check_arguments_test.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");
 #source("process_test_util.dart");
 
 test(args) {
-  Process process = new Process.start(new Options().executable, args);
+  Process process = Process.start(new Options().executable, args);
   // Wait for the process to exit and then check result.
   process.onExit = (exitCode) {
     Expect.equals(0, exitCode);
     process.close();
   };
 }
 
 main() {
   // Get the Dart script file which checks arguments.
   var scriptFile =
     new File("tests/standalone/io/process_check_arguments_script.dart");
   if (!scriptFile.existsSync()) {
     scriptFile =
         new File("../tests/standalone/io/process_check_arguments_script.dart");
   }
   test([scriptFile.name, '3', '0', 'a']);
   test([scriptFile.name, '3', '0', 'a b']);
   test([scriptFile.name, '3', '0', 'a\tb']);
   test([scriptFile.name, '3', '1', 'a\tb"']);
   test([scriptFile.name, '3', '1', 'a"\tb']);
   test([scriptFile.name, '3', '1', 'a"\t\\\\"b"']);
   test([scriptFile.name, '4', '0', 'a\tb', 'a']);
   test([scriptFile.name, '4', '0', 'a\tb', 'a\t\t\t\tb']);
   test([scriptFile.name, '4', '0', 'a\tb', 'a    b']);
 }