Centralizes more shared code between ash and mash

ash/aura/wm_root_window_controller_aura.h

Index: ash/aura/wm_root_window_controller_aura.h
diff --git a/ash/aura/wm_root_window_controller_aura.h b/ash/aura/wm_root_window_controller_aura.h
index 17c8b0756e64833ecfe79dc45cc2f7510c01650e..0b8883973db106091f94ebe4bda4407d7927b03d 100644
--- a/ash/aura/wm_root_window_controller_aura.h
+++ b/ash/aura/wm_root_window_controller_aura.h
@@ -32,7 +32,6 @@ class ASH_EXPORT WmRootWindowControllerAura : public WmRootWindowController {
   // WmRootWindowController:
   bool HasShelf() override;
   WmShell* GetShell() override;
-  AlwaysOnTopController* GetAlwaysOnTopController() override;
   WmShelf* GetShelf() override;
   WmWindow* GetWindow() override;
   void ConfigureWidgetInitParamsForContainer(
@@ -44,6 +43,10 @@ class ASH_EXPORT WmRootWindowControllerAura : public WmRootWindowController {
   void OnInitialWallpaperAnimationStarted() override;
   void OnWallpaperAnimationFinished(views::Widget* widget) override;
 
+ protected:
+  // WmRootWindowController:
+  bool ShouldDestroyWindowInCloseChildWindows(WmWindow* window) override;
+
  private:
   friend class RootWindowController;