Add a skeleton Start Page to the experimental app list.

ui/app_list/views/app_list_main_view.cc

Index: ui/app_list/views/app_list_main_view.cc
diff --git a/ui/app_list/views/app_list_main_view.cc b/ui/app_list/views/app_list_main_view.cc
index b6255a0e4eec10460decf4829543adbd4f8a6c4f..fde4a329577cd9c410106f0782c0f9ad53b9a5dc 100644
--- a/ui/app_list/views/app_list_main_view.cc
+++ b/ui/app_list/views/app_list_main_view.cc
@@ -22,7 +22,6 @@
 #include "ui/app_list/views/app_list_item_view.h"
 #include "ui/app_list/views/apps_container_view.h"
 #include "ui/app_list/views/contents_switcher_view.h"
-#include "ui/app_list/views/contents_view.h"
 #include "ui/app_list/views/search_box_view.h"
 #include "ui/views/controls/textfield/textfield.h"
 #include "ui/views/layout/box_layout.h"
@@ -165,6 +164,17 @@ void AppListMainView::ModelChanged() {
   Layout();
 }
 
+void AppListMainView::OnContentsViewShowStateChanged() {
+  search_box_view_->SetVisible(contents_view_->show_state() !=
+                               ContentsView::SHOW_START_PAGE);
+}
+
+void AppListMainView::OnStartPageSearchButtonPressed() {
+  search_box_view_->SetVisible(true);
+  search_box_view_->ClearSearch();
+  search_box_view_->RequestFocus();
+}
+
 void AppListMainView::SetDragAndDropHostOfCurrentAppList(
     ApplicationDragAndDropHost* drag_and_drop_host) {
   contents_view_->SetDragAndDropHostOfCurrentAppList(drag_and_drop_host);