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

chrome/browser/ui/webui/md_settings_ui.h

Index: chrome/browser/ui/webui/md_settings_ui.h
diff --git a/chrome/browser/ui/webui/md_settings_ui.h b/chrome/browser/ui/webui/md_settings_ui.h
index 3630a3a63f991a573bacdf1e507461c436280bbc..cba3563ac1110cb98cb6a9d8dec79e7531c9cad1 100644
--- a/chrome/browser/ui/webui/md_settings_ui.h
+++ b/chrome/browser/ui/webui/md_settings_ui.h
@@ -5,15 +5,24 @@
 #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.
+  void InitializeHandlers() override;
+  void OnFinishedLoading() override;
+
  private:
+  options::CoreOptionsHandler* core_handler_;
+
   DISALLOW_COPY_AND_ASSIGN(MdSettingsUI);
 };