Fetch and actually set prefs (using chrome.send for now).

chrome/browser/ui/webui/md_settings_ui.h

 // Copyright (c) 2012 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_MD_SETTINGS_UI_H_
 #define CHROME_BROWSER_UI_WEBUI_MD_SETTINGS_UI_H_
 
+#include "chrome/browser/ui/webui/options/core_options_handler.h"
+#include "chrome/browser/ui/webui/options/options_ui.h"
 #include "content/public/browser/web_ui_controller.h"
 
 // The WebUI handler for chrome://md-settings.
-class MdSettingsUI : public content::WebUIController {
+class MdSettingsUI : public content::WebUIController,
+                     public options::OptionsPageUIHandlerHost {
  public:
   explicit MdSettingsUI(content::WebUI* web_ui);
   ~MdSettingsUI() override;
 
+  // OptionsPageUIHandlerHost implementation.

[Dan Beam, 2015/03/19 23:47:09]

just

  // OptionsPageUIHandlerHost:

[Jeremy Klein, 2015/03/20 00:45:38]

Done.

+  void InitializeHandlers() override;
+  void OnFinishedLoading() override;
+
  private:
+  options::CoreOptionsHandler* core_handler_;
+
   DISALLOW_COPY_AND_ASSIGN(MdSettingsUI);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_MD_SETTINGS_UI_H_