Start splitting out WebUI into an implementation class and an interface that each page implements...

chrome/browser/ui/webui/sync_promo/sync_promo_ui.h

Index: chrome/browser/ui/webui/sync_promo/sync_promo_ui.h
===================================================================
--- chrome/browser/ui/webui/sync_promo/sync_promo_ui.h	(revision 117388)
+++ chrome/browser/ui/webui/sync_promo/sync_promo_ui.h	(working copy)
@@ -7,12 +7,13 @@
 #pragma once
 
 #include "content/browser/webui/web_ui.h"
+#include "content/public/browser/web_ui_controller.h"
 
 class Profile;
 class PrefService;
 
 // The Web UI handler for chrome://syncpromo.
-class SyncPromoUI : public WebUI {
+class SyncPromoUI : public WebUI, public content::WebUIController {
  public:
   // Constructs a SyncPromoUI. |contents| is the WebContents that this WebUI is
   // associated with. |contents| may not be NULL.