fix property linkage warnings

ash/wm/property_util.h

 // 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.
 
 #ifndef ASH_WM_PROPERTY_UTIL_H_
 #define ASH_WM_PROPERTY_UTIL_H_
 #pragma once
 
 #include "ash/ash_export.h"
 
 namespace aura {
 class Window;
-template<typename T>
-struct WindowProperty;
 }
 
 namespace gfx {
 class Rect;
 }
 
 namespace ash {
 
 // Sets the restore bounds property on |window|. Deletes existing bounds value
 // if exists.
 ASH_EXPORT void SetRestoreBounds(aura::Window* window, const gfx::Rect& bounds);
 
 // Same as SetRestoreBounds(), but does nothing if the restore bounds have
 // already been set. The bounds used are the bounds of the window.
 ASH_EXPORT void SetRestoreBoundsIfNotSet(aura::Window* window);
 
 // Returns the restore bounds property on |window|. NULL if the
 // restore bounds property does not exist for |window|. |window|
 // owns the bounds object.
 ASH_EXPORT const gfx::Rect* GetRestoreBounds(aura::Window* window);
 
 // Deletes and clears the restore bounds property on |window|.
 ASH_EXPORT void ClearRestoreBounds(aura::Window* window);
 
 // Toggles the maximized state of the specified window.
 ASH_EXPORT void ToggleMaximizedState(aura::Window* window);
 
-ASH_EXPORT extern const aura::WindowProperty<bool>* const
-    kWindowTrackedByWorkspacePropKey;
-
 enum WindowPersistsAcrossAllWorkspacesType {
   WINDOW_PERSISTS_ACROSS_ALL_WORKSPACES_VALUE_DEFAULT,
   WINDOW_PERSISTS_ACROSS_ALL_WORKSPACES_VALUE_NO,
   WINDOW_PERSISTS_ACROSS_ALL_WORKSPACES_VALUE_YES,
 };
 
-ASH_EXPORT extern const
-    aura::WindowProperty<WindowPersistsAcrossAllWorkspacesType>* const
-    kWindowPersistsAcrossAllWorkspacesPropKey;
-
 // Sets whether the specified window is tracked by workspace code. Default is
 // true. If set to false the workspace does not switch the current workspace,
 // nor does it attempt to impose constraints on the bounds of the window. This
 // is intended for tab dragging.
 ASH_EXPORT void SetTrackedByWorkspace(aura::Window* window, bool value);
 ASH_EXPORT bool GetTrackedByWorkspace(aura::Window* window);
 
 // Makes |window| persist across all workspaces. The default is controlled
 // by SetDefaultPersistsAcrossAllWorkspaces().
 ASH_EXPORT void SetPersistsAcrossAllWorkspaces(
     aura::Window* window,
     WindowPersistsAcrossAllWorkspacesType type);
 ASH_EXPORT bool GetPersistsAcrossAllWorkspaces(aura::Window* window);
 
 // Sets the default value for whether windows persist across all workspaces.
 // The default is false.
 ASH_EXPORT void SetDefaultPersistsAcrossAllWorkspaces(bool value);
 
 }
 
 #endif  // ASH_WM_PROPERTY_UTIL_H_