Upstream chrome://flags & chrome://ui-alternatives iOS WebUI.

ios/chrome/browser/ui/webui/flags_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 IOS_CHROME_BROWSER_UI_WEBUI_CRASHES_UI_H_
-#define IOS_CHROME_BROWSER_UI_WEBUI_CRASHES_UI_H_
+#ifndef IOS_CHROME_BROWSER_UI_WEBUI_FLAGS_UI_H_
+#define IOS_CHROME_BROWSER_UI_WEBUI_FLAGS_UI_H_
 
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "ios/public/provider/web/web_ui_ios_controller.h"
 #include "ui/base/layout.h"
 
 namespace base {
 class RefCountedMemory;
 }
 
-namespace web {
-class WebUIIOS;
-}
+class BaseFlagsUI : public web::WebUIIOSController {
+ public:
+  enum FlagsUIKind {
+    FLAGS_UI_GENERIC,
+    FLAGS_UI_APPLE,
+  };
 
-class CrashesUI : public web::WebUIIOSController {
- public:
-  explicit CrashesUI(web::WebUIIOS* web_ui);
+  BaseFlagsUI(web::WebUIIOS* web_ui, FlagsUIKind flags_ui_kind);
+  ~BaseFlagsUI() override;
 
   static base::RefCountedMemory* GetFaviconResourceBytes(
       ui::ScaleFactor scale_factor);
 
  private:
-  DISALLOW_COPY_AND_ASSIGN(CrashesUI);
+  void Initialize(web::WebUIIOS* web_ui, FlagsUIKind flags_ui_kind);
+
+  base::WeakPtrFactory<BaseFlagsUI> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(BaseFlagsUI);
 };
 
-#endif  // CHROME_BROWSER_UI_WEBUI_CRASHES_UI_H_
+class FlagsUI : public BaseFlagsUI {
+ public:
+  explicit FlagsUI(web::WebUIIOS* web_ui);
+  ~FlagsUI() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(FlagsUI);
+};
+
+class AppleFlagsUI : public BaseFlagsUI {
+ public:
+  explicit AppleFlagsUI(web::WebUIIOS* web_ui);
+  ~AppleFlagsUI() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(AppleFlagsUI);
+};
+
+#endif  // IOS_CHROME_BROWSER_UI_WEBUI_FLAGS_UI_H_