Add a skeleton Start Page to the experimental app list.

ui/app_list/views/apps_grid_view.cc

Index: ui/app_list/views/apps_grid_view.cc
diff --git a/ui/app_list/views/apps_grid_view.cc b/ui/app_list/views/apps_grid_view.cc
index f5c1adc0998b94f19d04ff2be3627a77b5ea0b59..6130af8f733ef4cd30fcc09bc57a2b36bfc56863 100644
--- a/ui/app_list/views/apps_grid_view.cc
+++ b/ui/app_list/views/apps_grid_view.cc
@@ -340,7 +340,7 @@ AppsGridView::AppsGridView(AppsGridViewDelegate* delegate,
   pagination_model_->AddObserver(this);
   AddChildView(page_switcher_view_);
 
-  if (start_page_contents) {
+  if (start_page_contents && app_list::switches::IsStartPageWebUIEnabled()) {
     start_page_view_ =
         new views::WebView(start_page_contents->GetBrowserContext());
     start_page_view_->SetWebContents(start_page_contents);