Centralizes more shared code between ash and mash

ash/mus/bridge/wm_root_window_controller_mus.h

Index: ash/mus/bridge/wm_root_window_controller_mus.h
diff --git a/ash/mus/bridge/wm_root_window_controller_mus.h b/ash/mus/bridge/wm_root_window_controller_mus.h
index 02a1482a5952b6e5917720cce209be31b8b44c4d..ebc5ac3eeb4fc2a37a790740b1b8bace579c53dc 100644
--- a/ash/mus/bridge/wm_root_window_controller_mus.h
+++ b/ash/mus/bridge/wm_root_window_controller_mus.h
@@ -48,10 +48,12 @@ class WmRootWindowControllerMus : public WmRootWindowController {
 
   const display::Display& GetDisplay() const;
 
+  // Exposed as public so WindowManager can call it.
+  void MoveWindowsTo(WmWindow* dest);
+
   // WmRootWindowController:
   bool HasShelf() override;
   WmShell* GetShell() override;
-  AlwaysOnTopController* GetAlwaysOnTopController() override;
   WmShelf* GetShelf() override;
   WmWindow* GetWindow() override;
   void ConfigureWidgetInitParamsForContainer(
@@ -64,6 +66,9 @@ class WmRootWindowControllerMus : public WmRootWindowController {
  private:
   friend class RootWindowController;
 
+  // WmRootWindowController:
+  bool ShouldDestroyWindowInCloseChildWindows(WmWindow* window) override;
+
   WmShellMus* shell_;
   RootWindowController* root_window_controller_;