Makes windowserver not send messages during shutdown

services/ui/ws/window_tree.h

 // Copyright 2014 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_WINDOW_TREE_H_
 #define SERVICES_UI_WS_WINDOW_TREE_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 133 matching lines @@
   WindowManagerState* window_manager_state() {
     return window_manager_state_.get();
   }
 
   DisplayManager* display_manager();
   const DisplayManager* display_manager() const;
 
   WindowServer* window_server() { return window_server_; }
   const WindowServer* window_server() const { return window_server_; }
 
+  // Called from ~WindowServer. Reset WindowTreeClient so that it no longer gets
+  // any messages.
+  void PrepareForWindowServerShutdown();
+
   // Adds a new root to this tree. This is only valid for window managers.
   void AddRootForWindowManager(const ServerWindow* root);
 
   // Invoked when a tree is about to be destroyed.
   void OnWindowDestroyingTreeImpl(WindowTree* tree);
 
   // These functions are synchronous variants of those defined in the mojom. The
   // WindowTree implementations all call into these. See the mojom for details.
   bool SetCapture(const ClientWindowId& client_window_id);
   bool ReleaseCapture(const ClientWindowId& client_window_id);
@@ skipping 399 matching lines @@
       waiting_for_top_level_window_info_;
   bool embedder_intercepts_events_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTree);
 };
 
 }  // namespace ws
 }  // namespace ui
 
 #endif  // SERVICES_UI_WS_WINDOW_TREE_H_