Changes to default apps promo per ui leads:

chrome/browser/dom_ui/shown_sections_handler.cc

 // Copyright (c) 2010 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.
 
 #include "chrome/browser/dom_ui/shown_sections_handler.h"
 
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/string_number_conversions.h"
 #include "base/values.h"
@@ skipping 29 matching lines @@
   }
 }
 
 }  // namespace
 
 // static
 int ShownSectionsHandler::GetShownSections(PrefService* prefs) {
   return prefs->GetInteger(prefs::kNTPShownSections);
 }
 
+// static
+void ShownSectionsHandler::SetShownSection(PrefService* prefs,
+                                           Section section) {
+  int shown_sections = GetShownSections(prefs);
+  shown_sections &= ~ALL_SECTIONS_MASK;
+  shown_sections |= section;
+  prefs->SetInteger(prefs::kNTPShownSections, shown_sections);
+}
+
 ShownSectionsHandler::ShownSectionsHandler(PrefService* pref_service)
     : pref_service_(pref_service) {
   pref_registrar_.Init(pref_service);
   pref_registrar_.Add(prefs::kNTPShownSections, this);
 }
 
 void ShownSectionsHandler::RegisterMessages() {
   dom_ui_->RegisterMessageCallback("getShownSections",
       NewCallback(this, &ShownSectionsHandler::HandleGetShownSections));
   dom_ui_->RegisterMessageCallback("setShownSections",
@@ skipping 82 matching lines @@
 
     // Hide any open sections.
     mode &= ~ALL_SECTIONS_MASK;
 
     // Show the apps section.
     mode |= APPS;
 
     prefs->SetInteger(prefs::kNTPShownSections, mode);
   }
 }