Changes to default apps promo per ui leads:

chrome/browser/dom_ui/shown_sections_handler.h

Index: chrome/browser/dom_ui/shown_sections_handler.h
diff --git a/chrome/browser/dom_ui/shown_sections_handler.h b/chrome/browser/dom_ui/shown_sections_handler.h
index ad227b4d46e592ce0b3fc4647cb088d56ce9858e..41c7da831d8daca07de39b4d683001119df0a734 100644
--- a/chrome/browser/dom_ui/shown_sections_handler.h
+++ b/chrome/browser/dom_ui/shown_sections_handler.h
@@ -43,6 +43,10 @@ class ShownSectionsHandler : public DOMMessageHandler,
   // Helper to get the current shown sections.
   static int GetShownSections(PrefService* pref_service);
 
+  // Expands |section|, collapsing any previously expanded section. This is the
+  // same thing that happens if a user clicks on |section|.
+  static void SetShownSection(PrefService* prefs, Section section);
+
   // DOMMessageHandler implementation.
   virtual void RegisterMessages();