mash: remove more shell/shelf WmWindow usage.

ash/app_list/app_list_delegate_impl.cc

Index: ash/app_list/app_list_delegate_impl.cc
diff --git a/ash/app_list/app_list_delegate_impl.cc b/ash/app_list/app_list_delegate_impl.cc
index ee61b8023afd3dff3cac333fc48935c9efd2c49d..d179b03d8c2db42f1c65d37d364560ca98c7c9fa 100644
--- a/ash/app_list/app_list_delegate_impl.cc
+++ b/ash/app_list/app_list_delegate_impl.cc
@@ -10,6 +10,7 @@
 #include "ash/shelf/wm_shelf.h"
 #include "ash/shell.h"
 #include "ash/shell_port.h"
+#include "ash/wm_window.h"
 #include "ui/app_list/presenter/app_list.h"
 
 namespace ash {
@@ -24,7 +25,7 @@ AppListDelegateImpl::~AppListDelegateImpl() {
 
 void AppListDelegateImpl::OnAppListVisibilityChanged(bool visible,
                                                      int64_t display_id) {
-  WmWindow* root_window =
+  aura::Window* root_window =
       ShellPort::Get()->GetRootWindowForDisplayId(display_id);
   AppListButton* app_list_button =
       WmShelf::ForWindow(root_window)->shelf_widget()->GetAppListButton();