Move ownership of the AppListViewDelegate into the AppListService

ash/shell/shell_delegate_impl.cc

Index: ash/shell/shell_delegate_impl.cc
diff --git a/ash/shell/shell_delegate_impl.cc b/ash/shell/shell_delegate_impl.cc
index 02c6a27a2d5d75ac1cc1d24515a34ecd9f4ad1d5..fb8f6050dbe470fe175a1e29960f2d9abf65a1c6 100644
--- a/ash/shell/shell_delegate_impl.cc
+++ b/ash/shell/shell_delegate_impl.cc
@@ -22,6 +22,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/user_manager/user_info_impl.h"
+#include "ui/app_list/app_list_view_delegate.h"
 #include "ui/aura/window.h"
 #include "ui/wm/core/input_method_event_filter.h"
 
@@ -212,8 +213,10 @@ content::BrowserContext* ShellDelegateImpl::GetActiveBrowserContext() {
   return browser_context_;
 }
 
-app_list::AppListViewDelegate* ShellDelegateImpl::CreateAppListViewDelegate() {
-  return ash::shell::CreateAppListViewDelegate();
+app_list::AppListViewDelegate* ShellDelegateImpl::GetAppListViewDelegate() {
+  if (!app_list_view_delegate_)
+    app_list_view_delegate_.reset(ash::shell::CreateAppListViewDelegate());
+  return app_list_view_delegate_.get();
 }
 
 ShelfDelegate* ShellDelegateImpl::CreateShelfDelegate(ShelfModel* model) {