Change Process.start to return a future that completes with a

tests/standalone/io/process_broken_pipe_test.dart

Index: tests/standalone/io/process_broken_pipe_test.dart
diff --git a/tests/standalone/io/process_broken_pipe_test.dart b/tests/standalone/io/process_broken_pipe_test.dart
index 91cfdeac14e638bb88ed1772e6df3f636bee7008..e56ab14a9d54f6b916fc16720dbbe8b8f81e0d4e 100644
--- a/tests/standalone/io/process_broken_pipe_test.dart
+++ b/tests/standalone/io/process_broken_pipe_test.dart
@@ -10,15 +10,16 @@
 
 main() {
   // Running dart without arguments makes it close right away.
-  Process process = Process.start(new Options().executable, []);
+  var future = Process.start(new Options().executable, []);
+  future.then((process) {
+    // Ignore error on stdin.
+    process.stdin.onError = (e) => null;
 
-  // Ignore error on stdin.
-  process.stdin.onError = (e) => null;
-
-  // Write to the stdin after the process is terminated to test
-  // writing to a broken pipe.
-  process.onExit = (code) {
-    Expect.isFalse(process.stdin.write([0]));
-    process.close();
-  };
+    // Write to the stdin after the process is terminated to test
+    // writing to a broken pipe.
+    process.onExit = (code) {
+      Expect.isFalse(process.stdin.write([0]));
+      process.close();
+    };
+  });
 }