mash: Migrate shelf menus to wm common types

ash/sysui/shell_delegate_mus.cc

Index: ash/sysui/shell_delegate_mus.cc
diff --git a/ash/sysui/shell_delegate_mus.cc b/ash/sysui/shell_delegate_mus.cc
index cff237f799ec8a019f5dbc007ceeaadb0e68b123..bbab683596de4158a236e2ca36a4131cd5d6a10d 100644
--- a/ash/sysui/shell_delegate_mus.cc
+++ b/ash/sysui/shell_delegate_mus.cc
@@ -219,9 +219,9 @@ ShellDelegateMus::CreatePointerWatcherDelegate() {
   return base::WrapUnique(new PointerWatcherDelegateMus);
 }
 
-ui::MenuModel* ShellDelegateMus::CreateContextMenu(ash::Shelf* shelf,
+ui::MenuModel* ShellDelegateMus::CreateContextMenu(WmShelf* wm_shelf,
                                                    const ShelfItem* item) {
-  return new ContextMenuMus(shelf);
+  return new ContextMenuMus(wm_shelf);
 }
 
 GPUSupport* ShellDelegateMus::CreateGPUSupport() {