Makes WindowTree::DeleteWindow() unembed for roots

services/ui/ws/server_window_observer.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SERVICES_UI_WS_SERVER_WINDOW_OBSERVER_H_
 #define SERVICES_UI_WS_SERVER_WINDOW_OBSERVER_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 60 matching lines @@
                                               int32_t cursor_id) {}
 
   virtual void OnWindowTextInputStateChanged(ServerWindow* window,
                                              const ui::TextInputState& state) {}
 
   virtual void OnWindowSharedPropertyChanged(
       ServerWindow* window,
       const std::string& name,
       const std::vector<uint8_t>* new_data) {}
 
+  // Called when the window is no longer an embed root.
+  virtual void OnWindowEmbeddedAppDisconnected(ServerWindow* window) {}
+
   // Called when a transient child is added to |window|.
   virtual void OnTransientWindowAdded(ServerWindow* window,
                                       ServerWindow* transient_child) {}
 
   // Called when a transient child is removed from |window|.
   virtual void OnTransientWindowRemoved(ServerWindow* window,
                                         ServerWindow* transient_child) {}
 
  protected:
   virtual ~ServerWindowObserver() {}
 };
 
 }  // namespace ws
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_WS_SERVER_WINDOW_OBSERVER_H_