Removes a couple more functions from WmWindow

ash/wm/switchable_windows.cc

 // Copyright 2014 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/switchable_windows.h"
 
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/wm_window.h"
+#include "ui/aura/window.h"
 
 namespace ash {
 namespace wm {
 
 const int kSwitchableWindowContainerIds[] = {
     kShellWindowId_DefaultContainer, kShellWindowId_AlwaysOnTopContainer,
     kShellWindowId_PanelContainer, kShellWindowId_AppListContainer};
 
 const size_t kSwitchableWindowContainerIdsLength =
     arraysize(kSwitchableWindowContainerIds);
 
 bool IsSwitchableContainer(const WmWindow* window) {
   if (!window)
     return false;
-  const int shell_window_id = window->GetShellWindowId();
+  const int shell_window_id = window->aura_window()->id();
   for (size_t i = 0; i < kSwitchableWindowContainerIdsLength; ++i) {
     if (shell_window_id == kSwitchableWindowContainerIds[i])
       return true;
   }
   return false;
 }
 
 }  // namespace wm
 }  // namespace ash