Changes how window manager obtains WindowTree from mus

components/mus/ws/user_display_manager.cc

 // Copyright 2016 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 "components/mus/ws/user_display_manager.h"
 
 #include "components/mus/ws/display.h"
 #include "components/mus/ws/display_manager.h"
 #include "components/mus/ws/window_manager_state.h"
 
@@ skipping 34 matching lines @@
   if (test_observer_)
     CallOnDisplayChanged(wms, test_observer_);
 }
 
 void UserDisplayManager::AddDisplayManagerBinding(
     mojo::InterfaceRequest<mojom::DisplayManager> request) {
   display_manager_bindings_.AddBinding(this, std::move(request));
 }
 
 void UserDisplayManager::OnWillDestroyDisplay(Display* display) {
-  if (!display->GetWindowManagerStateForUser(user_id_)
-           ->got_frame_decoration_values()) {
+  const WindowManagerState* wms =
+      display->GetWindowManagerStateForUser(user_id_);
+  if (wms && !wms->got_frame_decoration_values())
     return;
-  }
 
   display_manager_observers_.ForAllPtrs(
       [this, &display](mojom::DisplayManagerObserver* observer) {
         observer->OnDisplayRemoved(display->id());
       });
   if (test_observer_)
     test_observer_->OnDisplayRemoved(display->id());
 }
 
 void UserDisplayManager::OnMouseCursorLocationChanged(const gfx::Point& point) {
@@ skipping 93 matching lines @@
     }
   }
   observer->OnDisplays(std::move(display_ptrs));
 }
 
 void UserDisplayManager::CallOnDisplayChanged(
     const WindowManagerState* wms,
     mojom::DisplayManagerObserver* observer) {
   mojo::Array<mojom::DisplayPtr> displays(1);
   displays[0] = wms->ToMojomDisplay();
-  display_manager_observers_.ForAllPtrs(
-      [&displays](mojom::DisplayManagerObserver* observer) {
-        observer->OnDisplaysChanged(displays.Clone());
-      });
-  if (test_observer_)
-    test_observer_->OnDisplaysChanged(displays.Clone());
+  observer->OnDisplaysChanged(displays.Clone());
 }
 
 void UserDisplayManager::AddObserver(
     mojom::DisplayManagerObserverPtr observer) {
   mojom::DisplayManagerObserver* observer_impl = observer.get();
   display_manager_observers_.AddPtr(std::move(observer));
   OnObserverAdded(observer_impl);
 }
 
 }  // namespace ws
 }  // namespace mus