Add rudimentary mash shelf functionality.

mash/shelf/shelf_application.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_
+#ifndef MASH_SHELF_SHELF_APPLICATION_H_
+#define MASH_SHELF_SHELF_APPLICATION_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 {
+namespace shelf {
 
-class SystemUI : public mojo::ApplicationDelegate {
+class ShelfApplication : public mojo::ApplicationDelegate {
  public:
-  SystemUI();
-  ~SystemUI() override;
+  ShelfApplication();
+  ~ShelfApplication() 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);
+  DISALLOW_COPY_AND_ASSIGN(ShelfApplication);
 };
 
-}  // namespace system_ui
+}  // namespace shelf
 }  // namespace mash
 
-#endif  // MASH_SYSTEM_UI_SYSTEM_UI_H_
+#endif  // MASH_SHELF_SHELF_APPLICATION_H_