Makes RootWindowController window creation in terms of common types

ash/wm/aura/wm_globals_aura.h

 // Copyright 2016 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.
 
 #ifndef ASH_WM_AURA_WM_GLOBALS_AURA_H_
 #define ASH_WM_AURA_WM_GLOBALS_AURA_H_
 
 #include <set>
 
 #include "ash/ash_export.h"
@@ skipping 12 matching lines @@
                                  public aura::client::ActivationChangeObserver,
                                  public WindowTreeHostManager::Observer,
                                  public ShellObserver {
  public:
   WmGlobalsAura();
   ~WmGlobalsAura() override;
 
   static WmGlobalsAura* Get();
 
   // WmGlobals:
+  WmWindow* NewContainerWindow() override;
   WmWindow* GetFocusedWindow() override;
   WmWindow* GetActiveWindow() override;
   WmWindow* GetPrimaryRootWindow() override;
   WmWindow* GetRootWindowForDisplayId(int64_t display_id) override;
   WmWindow* GetRootWindowForNewWindows() override;
   std::vector<WmWindow*> GetMruWindowList() override;
   std::vector<WmWindow*> GetMruWindowListIgnoreModals() override;
   bool IsForceMaximizeOnFirstRun() override;
   bool IsUserSessionBlocked() override;
   bool IsScreenLocked() override;
@@ skipping 37 matching lines @@
 
   base::ObserverList<WmOverviewModeObserver> overview_mode_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(WmGlobalsAura);
 };
 
 }  // namespace wm
 }  // namespace ash
 
 #endif  // ASH_WM_AURA_WM_GLOBALS_AURA_H_