chromeos: changes DisconnectedAppHandler to be associated with a single window

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 cd5494d382317acc83b1baa4c5a838958bcd7d7a..14d29f6ad5deadf4b37c20f07331f26092011645 100644
--- a/ash/mus/root_window_controller.h
+++ b/ash/mus/root_window_controller.h
@@ -7,7 +7,6 @@
 
 #include <memory>
 
-#include "ash/mus/disconnected_app_handler.h"
 #include "ash/root_window_controller.h"
 #include "services/ui/public/interfaces/window_manager_constants.mojom.h"
 #include "ui/display/display.h"
@@ -94,8 +93,6 @@ class RootWindowController {
 
   display::Display display_;
 
-  std::unique_ptr<DisconnectedAppHandler> disconnected_app_handler_;
-
   DISALLOW_COPY_AND_ASSIGN(RootWindowController);
 };