Change stdout/stderr to binary mode on Windows

tests/standalone/io/stdio_nonblocking_test.dart

 // Copyright (c) 2015, 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:convert";
 import "dart:io";
 
 import "package:expect/expect.dart";
 
 void main() {
   var script =
       Platform.script.resolve("stdio_nonblocking_script.dart").toFilePath();
   Process.run(Platform.executable,
               ['--checked', script],
               stdoutEncoding: ASCII,
               stderrEncoding: ASCII).then((result) {
                   print(result.stdout);
                   print(result.stderr);
     Expect.equals(1, result.exitCode);
-    if (Platform.isWindows) {
-      Expect.equals('stdout\r\n\r\ntuodts\r\nABCDEFGHIJKLM\r\n', result.stdout);
-      Expect.equals('stderr\r\n\r\nrredts\r\nABCDEFGHIJKLM\r\n', result.stderr);
-    } else {
-      Expect.equals('stdout\n\ntuodts\nABCDEFGHIJKLM\n', result.stdout);
-      Expect.equals('stderr\n\nrredts\nABCDEFGHIJKLM\n', result.stderr);
-    }
+    Expect.equals('stdout\n\ntuodts\nABCDEFGHIJKLM\n', result.stdout);
+    Expect.equals('stderr\n\nrredts\nABCDEFGHIJKLM\n', result.stderr);
   });
 }