ash: Move AppList support to ShelfWidget, expose ShelfWidget in WmShelf

ash/common/shelf/wm_shelf.cc

Index: ash/common/shelf/wm_shelf.cc
diff --git a/ash/common/shelf/wm_shelf.cc b/ash/common/shelf/wm_shelf.cc
index 5367c0f06fdbcdb633f3afbd1fc33e7c9fa53490..d56d4cb312b9de209b3711624117a1fdd6f1d4a3 100644
--- a/ash/common/shelf/wm_shelf.cc
+++ b/ash/common/shelf/wm_shelf.cc
@@ -47,6 +47,8 @@ void WmShelf::SetShelfLayoutManager(ShelfLayoutManager* manager) {
   DCHECK(manager);
   shelf_layout_manager_ = manager;
   shelf_layout_manager_->AddObserver(this);
+  DCHECK(manager->shelf_widget());
+  shelf_widget_ = manager->shelf_widget();
 }
 
 WmWindow* WmShelf::GetWindow() {
@@ -250,10 +252,6 @@ ShelfView* WmShelf::GetShelfViewForTesting() {
   return shelf_->shelf_view_for_testing();
 }
 
-ShelfWidget* WmShelf::GetShelfWidgetForTesting() {
-  return shelf_layout_manager_->shelf_widget();
-}
-
 WmShelf::WmShelf() {}
 
 WmShelf::~WmShelf() {}