Use correct output encoding in Process.runSync.

tests/standalone/io/process_run_test.dart

+// Copyright (c) 2013, 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 "package:expect/expect.dart";
+
+import "process_test_util.dart";
+
+
+void testProcessRunBinaryOutput() {
+  var result = Process.runSync(getProcessTestFileName(),
+                               const ["0", "0", "0", "0"],
+                               stdoutEncoding: null);
+  Expect.isTrue(result.stdout is List<int>);
+  Expect.isTrue(result.stderr is String);
+
+  result = Process.runSync(getProcessTestFileName(),
+                           const ["0", "0", "0", "0"],
+                           stderrEncoding: null);
+  Expect.isTrue(result.stdout is String);
+  Expect.isTrue(result.stderr is List<int>);
+
+  result = Process.runSync(getProcessTestFileName(),
+                           const ["0", "0", "0", "0"],
+                           stdoutEncoding: null,
+                           stderrEncoding: null);
+  Expect.isTrue(result.stdout is List<int>);
+  Expect.isTrue(result.stderr is List<int>);
+}
+
+
+void main() {
+  testProcessRunBinaryOutput();
+}