Cleanup ash shelf accessor functions.

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 fdb6e0743a9e4061e62362cea2fcfda3c5cf66ea..0b8591622d8ee79ae488d19b03e5290c4f9acacd 100644
--- a/ash/wm/panels/panel_layout_manager.cc
+++ b/ash/wm/panels/panel_layout_manager.cc
@@ -311,8 +311,8 @@ void PanelLayoutManager::SetShelf(Shelf* shelf) {
   DCHECK(!shelf_layout_manager_);
   shelf_ = shelf;
   shelf_->AddIconObserver(this);
-  if (shelf_->shelf_widget()) {
-    shelf_layout_manager_ = shelf_->shelf_widget()->shelf_layout_manager();
+  if (shelf_->shelf_layout_manager()) {
+    shelf_layout_manager_ = shelf_->shelf_layout_manager();
     WillChangeVisibilityState(shelf_layout_manager_->visibility_state());
     shelf_layout_manager_->AddObserver(this);
   }
@@ -584,8 +584,7 @@ void PanelLayoutManager::MinimizePanel(aura::Window* panel) {
   panel_slide_settings.SetTransitionDuration(
       base::TimeDelta::FromMilliseconds(kPanelSlideDurationMilliseconds));
   gfx::Rect bounds(panel->bounds());
-  bounds.Offset(GetSlideInAnimationOffset(
-      shelf_->shelf_widget()->GetAlignment()));
+  bounds.Offset(GetSlideInAnimationOffset(shelf_->alignment()));
   SetChildBoundsDirect(panel, bounds);
   panel->Hide();
   layer->SetOpacity(0);
@@ -618,7 +617,7 @@ void PanelLayoutManager::Relayout() {
     return;
   base::AutoReset<bool> auto_reset_in_layout(&in_layout_, true);
 
-  ShelfAlignment alignment = shelf_->shelf_widget()->GetAlignment();
+  ShelfAlignment alignment = shelf_->alignment();
   bool horizontal = alignment == SHELF_ALIGNMENT_TOP ||
                     alignment == SHELF_ALIGNMENT_BOTTOM;
   gfx::Rect shelf_bounds = ash::ScreenUtil::ConvertRectFromScreen(