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

tests/standalone/io/process_stderr_test.dart

Index: tests/standalone/io/process_stderr_test.dart
diff --git a/tests/standalone/io/process_stderr_test.dart b/tests/standalone/io/process_stderr_test.dart
index 47a030b49dc098de6b3e2a47310250282c0a1410..8c57880ac5a45d10c0957b6b97a53398c48268ac 100644
--- a/tests/standalone/io/process_stderr_test.dart
+++ b/tests/standalone/io/process_stderr_test.dart
@@ -57,8 +57,8 @@ void test(Process process, int expectedExitCode) {
 
 main() {
   // Run the test using the process_test binary.
-  test(new Process.start(getProcessTestFileName(),
-                         const ["1", "1", "99", "0"]), 99);
+  test(Process.start(getProcessTestFileName(),
+                     const ["1", "1", "99", "0"]), 99);
 
   // Run the test using the dart binary with an echo script.
   // The test runner can be run from either the root or from runtime.
@@ -67,5 +67,5 @@ main() {
     scriptFile = new File("../tests/standalone/io/process_std_io_script.dart");
   }
   Expect.isTrue(scriptFile.existsSync());
-  test(new Process.start(new Options().executable, [scriptFile.name, "1"]), 0);
+  test(Process.start(new Options().executable, [scriptFile.name, "1"]), 0);
 }