mash: Migrate shelf menus to wm common types

ash/sysui/shell_delegate_mus.h

Index: ash/sysui/shell_delegate_mus.h
diff --git a/ash/sysui/shell_delegate_mus.h b/ash/sysui/shell_delegate_mus.h
index d6a41e9068316313ddd7b24dbef765ca61e39ca7..5e50d074ac1c2d69e1c464ef2375ecfaff443a22 100644
--- a/ash/sysui/shell_delegate_mus.h
+++ b/ash/sysui/shell_delegate_mus.h
@@ -52,8 +52,8 @@ class ShellDelegateMus : public ash::ShellDelegate {
   std::unique_ptr<ContainerDelegate> CreateContainerDelegate() override;
   std::unique_ptr<PointerWatcherDelegate> CreatePointerWatcherDelegate()
       override;
-  ui::MenuModel* CreateContextMenu(ash::Shelf* shelf,
-                                   const ash::ShelfItem* item) override;
+  ui::MenuModel* CreateContextMenu(WmShelf* wm_shelf,
+                                   const ShelfItem* item) override;
   GPUSupport* CreateGPUSupport() override;
   base::string16 GetProductName() const override;
   gfx::Image GetDeprecatedAcceleratorImage() const override;