Fixes possible crash in ~Display

services/ui/ws/window_server.cc

 // 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.
 
 #include "services/ui/ws/window_server.h"
 
 #include <set>
 #include <string>
 
 #include "base/logging.h"
@@ skipping 142 matching lines @@
     auto iter = tree_map_.find(tree->id());
     DCHECK(iter != tree_map_.end());
     tree_ptr = std::move(iter->second);
     tree_map_.erase(iter);
   }
 
   // Notify remaining connections so that they can cleanup.
   for (auto& pair : tree_map_)
     pair.second->OnWindowDestroyingTreeImpl(tree);
 
-  // Notify the hosts, taking care to only notify each host once.
-  std::set<Display*> displays_notified;
-  for (auto* root : tree->roots()) {
-    // WindowTree holds its roots as a const, which is right as WindowTree
-    // doesn't need to modify the window. OTOH we do. We could look up the
-    // window using the id to get non-const version, but instead we cast.
-    Display* display =
-        display_manager_->GetDisplayContaining(const_cast<ServerWindow*>(root));
-    if (display && displays_notified.count(display) == 0) {
-      display->OnWillDestroyTree(tree);
-      displays_notified.insert(display);
-    }
-  }
-
   window_manager_window_tree_factory_set_.DeleteFactoryAssociatedWithTree(tree);
 
   // Remove any requests from the client that resulted in a call to the window
   // manager and we haven't gotten a response back yet.
   std::set<uint32_t> to_remove;
   for (auto& pair : in_flight_wm_change_map_) {
     if (pair.second.client_id == tree->id())
       to_remove.insert(pair.first);
   }
   for (uint32_t id : to_remove)
@@ skipping 646 matching lines @@
 void WindowServer::OnUserIdAdded(const UserId& id) {
   activity_monitor_map_[id] = base::MakeUnique<UserActivityMonitor>(nullptr);
 }
 
 void WindowServer::OnUserIdRemoved(const UserId& id) {
   activity_monitor_map_.erase(id);
 }
 
 }  // namespace ws
 }  // namespace ui