Make sure WindowObservers are removed from window before destruction

ash/wm/window_state.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/window_state.h"
 
 #include "ash/ash_switches.h"
 #include "ash/root_window_controller.h"
 #include "ash/screen_ash.h"
 #include "ash/shell_window_ids.h"
@@ skipping 261 matching lines @@
     window_show_type_ = ToWindowShowType(GetShowState());
     ui::WindowShowState old_state = static_cast<ui::WindowShowState>(old);
     // TODO(oshima): Notify only when the state has changed.
     // Doing so break a few tests now.
     FOR_EACH_OBSERVER(
         WindowStateObserver, observer_list_,
         OnWindowShowTypeChanged(this, ToWindowShowType(old_state)));
   }
 }
 
-void WindowState::OnWindowDestroying(aura::Window* window) {
-  window_->RemoveObserver(this);
-}
-
 void WindowState::SnapWindow(WindowShowType left_or_right,
                              const gfx::Rect& bounds) {
   // Compute the bounds that the window will restore to. If the window does not
   // already have restore bounds, it will be restored (when un-snapped) to the
   // last bounds that it had before getting snapped.
   gfx::Rect restore_bounds_in_screen(HasRestoreBounds() ?
       GetRestoreBoundsInScreen() : window_->GetBoundsInScreen());
   // Set the window's restore bounds so that WorkspaceLayoutManager knows
   // which width to use when the snapped window is moved to the edge.
   SetRestoreBoundsInParent(bounds);
@@ skipping 39 matching lines @@
   }
   return settings;
 }
 
 const WindowState* GetWindowState(const aura::Window* window) {
   return GetWindowState(const_cast<aura::Window*>(window));
 }
 
 }  // namespace wm
 }  // namespace ash