ash: Convert ShelfDelegate to use WmShelf* instead of Shelf*

ash/mus/bridge/wm_shelf_mus.cc

Index: ash/mus/bridge/wm_shelf_mus.cc
diff --git a/ash/mus/bridge/wm_shelf_mus.cc b/ash/mus/bridge/wm_shelf_mus.cc
index abbe426156a63a4117001d9189e260a122ce3f89..951ee63f196efa2978ceef27e5e05adf8ef9e1e1 100644
--- a/ash/mus/bridge/wm_shelf_mus.cc
+++ b/ash/mus/bridge/wm_shelf_mus.cc
@@ -28,7 +28,7 @@ WmShelfMus::WmShelfMus(WmRootWindowController* root_window_controller) {
   // Must be initialized before the delegate is notified because the delegate
   // may try to access the WmShelf.
   SetShelf(shelf_.get());
-  WmShell::Get()->shelf_delegate()->OnShelfCreated(shelf_.get());
+  WmShell::Get()->shelf_delegate()->OnShelfCreated(this);
   WmShell::Get()->NotifyShelfCreatedForRootWindow(root);
   shelf_widget_->PostCreateShelf();
 }