Centralizes more shared code between ash and mash

ash/mus/root_window_controller.h

Index: ash/mus/root_window_controller.h
diff --git a/ash/mus/root_window_controller.h b/ash/mus/root_window_controller.h
index 5f467a8c1e3503fe506b2be418c8ef43e9f98ac3..59c98b4a73bc9b8b2cfd3b830975cd68d55cd000 100644
--- a/ash/mus/root_window_controller.h
+++ b/ash/mus/root_window_controller.h
@@ -19,7 +19,6 @@ class Connector;
 
 namespace ash {
 
-class AlwaysOnTopController;
 class WorkspaceLayoutManager;
 
 namespace mus {
@@ -33,9 +32,7 @@ class WmTestHelper;
 class WmWindowMus;
 
 // RootWindowController manages the windows and state for a single display.
-// RootWindowController is tied to the lifetime of the ui::Window it is
-// created with. It is assumed the RootWindowController is deleted once the
-// associated ui::Window is destroyed.
+// RootWindowController takes ownership of the Window that it passed to it.
 class RootWindowController {
  public:
   RootWindowController(WindowManager* window_manager,
@@ -43,9 +40,14 @@ class RootWindowController {
                        const display::Display& display);
   ~RootWindowController();
 
+  void Shutdown();
+
   shell::Connector* GetConnector();
 
   ui::Window* root() { return root_; }
+  WmRootWindowControllerMus* wm_root_window_controller() {
+    return wm_root_window_controller_.get();
+  }
 
   ui::Window* NewTopLevelWindow(
       std::map<std::string, std::vector<uint8_t>>* properties);
@@ -62,10 +64,6 @@ class RootWindowController {
     return workspace_layout_manager_;
   }
 
-  AlwaysOnTopController* always_on_top_controller() {
-    return always_on_top_controller_.get();
-  }
-
   WmShelfMus* wm_shelf() { return wm_shelf_.get(); }
 
  private:
@@ -91,8 +89,6 @@ class RootWindowController {
   WorkspaceLayoutManager* workspace_layout_manager_ = nullptr;
   std::map<ui::Window*, std::unique_ptr<LayoutManager>> layout_managers_;
 
-  std::unique_ptr<AlwaysOnTopController> always_on_top_controller_;
-
   std::unique_ptr<DisconnectedAppHandler> disconnected_app_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(RootWindowController);