Add rudimentary mash shelf functionality.

mash/system_ui/system_ui.h

-// Copyright 2015 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 MASH_SYSTEM_UI_SYSTEM_UI_H_
-#define MASH_SYSTEM_UI_SYSTEM_UI_H_
-
-#include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
-#include "mojo/services/tracing/public/cpp/tracing_impl.h"
-#include "mojo/shell/public/cpp/application_delegate.h"
-
-namespace views {
-class AuraInit;
-}
-
-namespace mash {
-namespace system_ui {
-
-class SystemUI : public mojo::ApplicationDelegate {
- public:
-  SystemUI();
-  ~SystemUI() override;
-
- private:
-  // mojo::ApplicationDelegate:
-  void Initialize(mojo::ApplicationImpl* app) override;
-  bool ConfigureIncomingConnection(
-      mojo::ApplicationConnection* connection) override;
-
-  mojo::TracingImpl tracing_;
-
-  scoped_ptr<views::AuraInit> aura_init_;
-
-  DISALLOW_COPY_AND_ASSIGN(SystemUI);
-};
-
-}  // namespace system_ui
-}  // namespace mash
-
-#endif  // MASH_SYSTEM_UI_SYSTEM_UI_H_