Makes Panel related classes use ash/wm/common types

ash/wm/drag_window_resizer.cc

 // Copyright (c) 2012 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/drag_window_resizer.h"
 
 #include "ash/display/mouse_cursor_event_filter.h"
 #include "ash/screen_util.h"
 #include "ash/shell.h"
 #include "ash/wm/common/window_positioning_utils.h"
@@ skipping 148 matching lines @@
   GetAuraTarget()->layer()->SetOpacity(opacity);
   drag_window_controller_->Update(bounds_in_screen, drag_location_in_screen);
 }
 
 bool DragWindowResizer::ShouldAllowMouseWarp() {
   return details().window_component == HTCAPTION &&
          !::wm::GetTransientParent(GetAuraTarget()) &&
          wm::IsWindowUserPositionable(GetAuraTarget());
 }
 
+aura::Window* DragWindowResizer::GetAuraTarget() {
+  return wm::WmWindowAura::GetAuraWindow(GetTarget());
+}
+
 }  // namespace ash