ash: Move shelf alignment and auto-hide calls from Shell to Shelf

ash/mus/shelf_delegate_mus.cc

Index: ash/mus/shelf_delegate_mus.cc
diff --git a/ash/mus/shelf_delegate_mus.cc b/ash/mus/shelf_delegate_mus.cc
index 3fa2e0e2b6ea8ce501ae8ebd92fc9cba79a7a134..7626cbcdee7653935c97e1954a77ddf09811d6e9 100644
--- a/ash/mus/shelf_delegate_mus.cc
+++ b/ash/mus/shelf_delegate_mus.cc
@@ -286,14 +286,13 @@ void ShelfDelegateMus::AddObserver(
 
 void ShelfDelegateMus::SetAlignment(mash::shelf::mojom::Alignment alignment) {
   wm::ShelfAlignment value = static_cast<wm::ShelfAlignment>(alignment);
-  Shell::GetInstance()->SetShelfAlignment(value, Shell::GetPrimaryRootWindow());
+  Shelf::ForPrimaryDisplay()->SetAlignment(value);
 }
 
 void ShelfDelegateMus::SetAutoHideBehavior(
     mash::shelf::mojom::AutoHideBehavior auto_hide) {
   ShelfAutoHideBehavior value = static_cast<ShelfAutoHideBehavior>(auto_hide);
-  Shell::GetInstance()->SetShelfAutoHideBehavior(value,
-                                                 Shell::GetPrimaryRootWindow());
+  Shelf::ForPrimaryDisplay()->SetAutoHideBehavior(value);
 }
 
 void ShelfDelegateMus::PinItem(