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

tests/standalone/io/process_start_exception_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.
 //
 // Process test program to errors during startup of the process.
 
 #import("dart:io");
 
 testStartError() {
-  Process process =
-      new Process.start("__path_to_something_that_should_not_exist__",
-                        const []);
+  Process process = Process.start("__path_to_something_that_should_not_exist__",
+                                  const []);
 
   process.onExit = (int exitCode) {
     Expect.fail("exit handler called");
   };
 
   process.onError = (ProcessException e) {
     Expect.equals(2, e.errorCode, e.toString());
   };
 }
 
 
 testRunError() {
-  Process process =
-      new Process.run("__path_to_something_that_should_not_exist__",
-                      const [],
-                      null,
-                      (exit, out, err) {
-    Expect.fail("exit handler called");
+  Future<ProcessResult> processFuture =
+      Process.run("__path_to_something_that_should_not_exist__",
+                  const []);
+
+  processFuture.then((result) => Expect.fail("exit handler called"));
+
+  processFuture.handleException((e) {
+    Expect.isTrue(e is ProcessException);
+    Expect.equals(2, e.errorCode, e.toString());
+    return true;
   });
-
-  process.onError = (ProcessException e) {
-    Expect.equals(2, e.errorCode, e.toString());
-  };
 }
 
 main() {
   testStartError();
   testRunError();
 }