fix property linkage warnings

ash/wm/property_util.h

Index: ash/wm/property_util.h
diff --git a/ash/wm/property_util.h b/ash/wm/property_util.h
index 7e1820e7a0c54a55cbb08ea15a6ad754fbb0b223..ce0940b8964ef5737c74f7cab5cbb21cd20f0276 100644
--- a/ash/wm/property_util.h
+++ b/ash/wm/property_util.h
@@ -10,8 +10,6 @@
 
 namespace aura {
 class Window;
-template<typename T>
-struct WindowProperty;
 }
 
 namespace gfx {
@@ -39,19 +37,12 @@ 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