Gets chrome --mus some what working

ash/public/cpp/config.h

+// 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.
+
+#ifndef ASH_PUBLIC_CPP_APP_CONFIG_H_
+#define ASH_PUBLIC_CPP_APP_CONFIG_H_
+
+namespace ash {
+
+// Enumeration of the possible configurations supported by ash.
+enum class Config {
+  // Classic mode does not use mus.
+  CLASSIC,
+
+  // Aura is backed by mus, but chrome and ash are still in the same process.
+  MUS,
+
+  // Aura is backed by mus and chrome and ash are in separate processes. In this
+  // mode chrome code can only use ash code in ash/public/cpp.
+  MASH,
+};
+
+}  // namespace ash
+
+#endif  // ASH_PUBLIC_CPP_APP_CONFIG_H_