MD Settings: add a semi-functional System page

chrome/browser/ui/webui/settings/system_handler.h

+// Copyright 2016 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_SETTINGS_SYSTEM_HANDLER_H_
+#define CHROME_BROWSER_UI_WEBUI_SETTINGS_SYSTEM_HANDLER_H_
+
+#include "base/macros.h"
+#include "chrome/browser/ui/webui/settings/md_settings_ui.h"
+
+namespace base {
+class ListValue;
+}
+
+namespace settings {
+
+class SystemHandler : public SettingsPageUIHandler {
+ public:
+  SystemHandler();
+  ~SystemHandler() override;
+
+  // SettingsPageUIHandler:
+  void RegisterMessages() override;
+
+ private:
+  // Handler for the "changeProxySettings" message. No args.
+  void HandleChangeProxySettings(const base::ListValue* /*args*/);
+
+  DISALLOW_COPY_AND_ASSIGN(SystemHandler);
+};
+
+}  // namespace settings
+
+#endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_SYSTEM_HANDLER_H_