Change ContentsView::SetActivePage to use States rather than indexes.

ui/app_list/views/start_page_view.cc

Index: ui/app_list/views/start_page_view.cc
diff --git a/ui/app_list/views/start_page_view.cc b/ui/app_list/views/start_page_view.cc
index 26b52061fd3cddf70107d62336adfe4db0de411b..58a8f59f67bc3fd04a480ec12fda4a255ab9c198 100644
--- a/ui/app_list/views/start_page_view.cc
+++ b/ui/app_list/views/start_page_view.cc
@@ -231,9 +231,7 @@ void StartPageView::MaybeOpenCustomLauncherPage() {
   if (!app_list_main_view_->ShouldShowCustomLauncherPage())
     return;
 
-  int custom_page_index = contents_view->GetPageIndexForState(
-      AppListModel::STATE_CUSTOM_LAUNCHER_PAGE);
-  contents_view->SetActivePage(custom_page_index);
+  contents_view->SetActivePage(AppListModel::STATE_CUSTOM_LAUNCHER_PAGE);
 }
 
 void StartPageView::Reset() {