[Chromoting] Add a simple Windows app that registers and starts a host.

remoting/host/setup/pin_validator.cc

Index: remoting/host/setup/pin_validator.cc
diff --git a/remoting/host/setup/pin_validator.cc b/remoting/host/setup/pin_validator.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ce753a4a50ab9c4fecc65b57cb34360039c2261e
--- /dev/null
+++ b/remoting/host/setup/pin_validator.cc
@@ -0,0 +1,20 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/host/setup/pin_validator.h"
+
+namespace remoting {
+
+bool IsPinValid(const std::string& pin) {
+  if (pin.length() < 6)
+    return false;
+  for (size_t i = 0; i < pin.length(); i++) {
+    char c = pin[i];
+    if (c < '0'  || c > '9')
+      return false;
+  }
+  return true;
+}
+
+}  // namespace remoting