Adds WmWindow and converts WindowState to use it

ash/wm/panels/panel_window_event_handler.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/panels/panel_window_event_handler.h"
 
 #include "ash/metrics/user_metrics_recorder.h"
 #include "ash/shell.h"
 #include "ash/wm/window_state.h"
+#include "ash/wm/window_state_aura.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_delegate.h"
 #include "ui/base/hit_test.h"
 #include "ui/events/event.h"
 
 namespace ash {
 
 PanelWindowEventHandler::PanelWindowEventHandler() {
 }
 
@@ skipping 25 matching lines @@
           HTCAPTION) {
     ash::Shell::GetInstance()->metrics()->RecordUserMetricsAction(
         ash::UMA_PANEL_MINIMIZE_CAPTION_GESTURE);
     wm::GetWindowState(target)->Minimize();
     event->StopPropagation();
     return;
   }
 }
 
 }  // namespace ash