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

ash/sysui/shelf_delegate_mus.cc

Index: ash/sysui/shelf_delegate_mus.cc
diff --git a/ash/sysui/shelf_delegate_mus.cc b/ash/sysui/shelf_delegate_mus.cc
index d41b36f9fb3d3bdba517558c96cf232be4d72b77..3855cc621e12412968f8ee616aad8b0e0f2c6a23 100644
--- a/ash/sysui/shelf_delegate_mus.cc
+++ b/ash/sysui/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(