Moves management of transients out of Window

ash/wm/mru_window_tracker.cc

 // Copyright 2013 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 "ash/wm/mru_window_tracker.h"
 
 #include <algorithm>
 
 #include "ash/session_state_delegate.h"
 #include "ash/shell.h"
@@ skipping 172 matching lines @@
   CHECK(active_window->layer());
   mru_windows_.push_front(active_window);
 }
 
 void MruWindowTracker::OnWindowActivated(aura::Window* gained_active,
                                          aura::Window* lost_active) {
   if (!ignore_window_activations_)
     SetActiveWindow(gained_active);
 }
 
-void MruWindowTracker::OnWindowDestroying(aura::Window* window) {
+void MruWindowTracker::OnWindowDestroyed(aura::Window* window) {
+  // It's possible for OnWindowActivated() to be called after
+  // OnWindowDestroying(). This means we need to override OnWindowDestroyed()
+  // else we may end up with a deleted window in |mru_windows_|.
   mru_windows_.remove(window);
   window->RemoveObserver(this);
 }
 
 }  // namespace ash