mash: improves browser frame decorations

ash/public/cpp/window_style.cc

Index: ash/public/cpp/window_style.cc
diff --git a/ash/public/cpp/window_style.cc b/ash/public/cpp/window_style.cc
new file mode 100644
index 0000000000000000000000000000000000000000..375d770af6d524490972fbe7010ac384bbc668ef
--- /dev/null
+++ b/ash/public/cpp/window_style.cc
@@ -0,0 +1,16 @@
+// Copyright 2017 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 "ash/public/cpp/window_style.h"
+
+#include "ash/public/interfaces/window_style.mojom.h"
+
+namespace ash {
+
+bool IsValidWindowStyle(int32_t type) {
+  return type == static_cast<int32_t>(mojom::WindowStyle::DEFAULT) ||
+         type == static_cast<int32_t>(mojom::WindowStyle::BROWSER);
+}
+
+}  // namespace ash