mash: Migrate ScopedTargetRootWindow to //ash/common

ash/shelf/shelf_view.h

Index: ash/shelf/shelf_view.h
diff --git a/ash/shelf/shelf_view.h b/ash/shelf/shelf_view.h
index 8af3d1e4882ceaef8a3df332948e784c3b0fe990..9b8e1122da2ed326492de35aece0ad732be597bf 100644
--- a/ash/shelf/shelf_view.h
+++ b/ash/shelf/shelf_view.h
@@ -42,7 +42,7 @@ class AppListButton;
 class DragImageView;
 class OverflowBubble;
 class OverflowButton;
-class ScopedTargetRootWindow;
+class ScopedRootWindowForNewWindows;
 class Shelf;
 class ShelfButton;
 class ShelfDelegate;
@@ -397,7 +397,8 @@ class ASH_EXPORT ShelfView : public views::View,
   std::unique_ptr<ui::MenuModel> menu_model_;
   std::unique_ptr<views::MenuModelAdapter> menu_model_adapter_;
   std::unique_ptr<views::MenuRunner> launcher_menu_runner_;
-  std::unique_ptr<ScopedTargetRootWindow> scoped_target_root_window_;
+  std::unique_ptr<ScopedRootWindowForNewWindows>
+      scoped_root_window_for_new_windows_;
 
   base::ObserverList<ShelfIconObserver> observers_;