Demo UI made with a help of WUG toolkit (DO NOT SEND TO CQ).

chrome/browser/ui/webui/demo_ui/demo.h

Index: chrome/browser/ui/webui/demo_ui/demo.h
diff --git a/chrome/browser/ui/webui/demo_ui/demo.h b/chrome/browser/ui/webui/demo_ui/demo.h
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+// 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 CHROME_BROWSER_UI_WEBUI_DEMO_UI_DEMO_H_
+#define CHROME_BROWSER_UI_WEBUI_DEMO_UI_DEMO_H_
+
+#include "base/macros.h"
+#include "components/demo_ui/demo_view_model.h"
+
+class Profile;
+
+class Demo : public gen::DemoViewModel {
+ public:
+  explicit Demo(Profile* profile);
+  ~Demo() override;
+
+  // Overridden from webui_generator::ViewModel:
+  void Initialize() override;
+
+  static void Register();
+
+ private:
+  Profile* profile_;
+
+  DISALLOW_COPY_AND_ASSIGN(Demo);
+};
+
+#endif  // CHROME_BROWSER_UI_WEBUI_DEMO_UI_DEMO_H_