ash: Explicitly teach various components about ShelfLayoutManager.

ash/wm/panels/panel_layout_manager.cc

Index: ash/wm/panels/panel_layout_manager.cc
diff --git a/ash/wm/panels/panel_layout_manager.cc b/ash/wm/panels/panel_layout_manager.cc
index 9694cc214f408646fb4fd01f5239e77b878a076d..fdb6e0743a9e4061e62362cea2fcfda3c5cf66ea 100644
--- a/ash/wm/panels/panel_layout_manager.cc
+++ b/ash/wm/panels/panel_layout_manager.cc
@@ -312,8 +312,7 @@ void PanelLayoutManager::SetShelf(Shelf* shelf) {
   shelf_ = shelf;
   shelf_->AddIconObserver(this);
   if (shelf_->shelf_widget()) {
-    shelf_layout_manager_ = ash::ShelfLayoutManager::ForShelf(
-        shelf_->shelf_widget()->GetNativeWindow());
+    shelf_layout_manager_ = shelf_->shelf_widget()->shelf_layout_manager();
     WillChangeVisibilityState(shelf_layout_manager_->visibility_state());
     shelf_layout_manager_->AddObserver(this);
   }