Removed webui_generator and new OOBE UI placeholder.

ui/oobe/oobe_md_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 UI_OOBE_OOBE_MD_UI_H_
-#define UI_OOBE_OOBE_MD_UI_H_
-
-#include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
-#include "content/public/browser/web_ui_controller.h"
-#include "ui/oobe/oobe_export.h"
-
-namespace content {
-class WebUI;
-}
-
-namespace gen {
-class OobeWebUIView;
-}
-
-class OOBE_EXPORT OobeMdUI : public content::WebUIController {
- public:
-  OobeMdUI(content::WebUI* web_ui, const std::string& host);
-  ~OobeMdUI() override;
-
- private:
-  scoped_ptr<gen::OobeWebUIView> view_;
-
-  DISALLOW_COPY_AND_ASSIGN(OobeMdUI);
-};
-
-#endif  // UI_OOBE_OOBE_MD_UI_H_