ash: Remove ash::Shelf in favor of ash::WmShelf

ash/common/shelf/shelf_layout_manager.cc

Index: ash/common/shelf/shelf_layout_manager.cc
diff --git a/ash/common/shelf/shelf_layout_manager.cc b/ash/common/shelf/shelf_layout_manager.cc
index eb25188a57740c3bd8bb68986b69131f2f9fb495..6761f97ac4325969a19b817b38fde3adae7771c7 100644
--- a/ash/common/shelf/shelf_layout_manager.cc
+++ b/ash/common/shelf/shelf_layout_manager.cc
@@ -240,7 +240,7 @@ void ShelfLayoutManager::UpdateVisibilityState() {
   WmWindow* shelf_window = WmLookup::Get()->GetWindowForWidget(shelf_widget_);
   WmRootWindowController* controller = shelf_window->GetRootWindowController();
   // Bail out early before the shelf is initialized or after it is destroyed.
-  if (!controller || !shelf_widget_->shelf() || in_shutdown_)
+  if (!controller || !wm_shelf_->IsShelfInitialized() || in_shutdown_)
     return;
   bool was_invisible_auto_hide_shelf = invisible_auto_hide_shelf_;
   // Always reset to be safe.
@@ -888,7 +888,7 @@ gfx::Rect ShelfLayoutManager::GetAutoHideShowShelfRegionInScreen() const {
 
 ShelfAutoHideState ShelfLayoutManager::CalculateAutoHideState(
     ShelfVisibilityState visibility_state) const {
-  if (visibility_state != SHELF_AUTO_HIDE || !shelf_widget_->shelf())
+  if (visibility_state != SHELF_AUTO_HIDE || !wm_shelf_->IsShelfInitialized())
     return SHELF_AUTO_HIDE_HIDDEN;
 
   const int64_t shelf_display_id = WmLookup::Get()