[NOT FOR REVIEW] ash: Add some implementation for the window management extension API.

ash/shell/shell_delegate_impl.h

Index: ash/shell/shell_delegate_impl.h
diff --git a/ash/shell/shell_delegate_impl.h b/ash/shell/shell_delegate_impl.h
index 55880f3088d0b27b0dba9695d70c02a609266b8c..655bde24a7a2d1317a3968fc4d0b9d36dc23a316 100644
--- a/ash/shell/shell_delegate_impl.h
+++ b/ash/shell/shell_delegate_impl.h
@@ -47,6 +47,8 @@ class ShellDelegateImpl : public ash::ShellDelegate {
       ash::SystemTray* tray) OVERRIDE;
   virtual ash::UserWallpaperDelegate* CreateUserWallpaperDelegate() OVERRIDE;
   virtual aura::client::UserActionClient* CreateUserActionClient() OVERRIDE;
+  virtual ash::WindowManagerExtensionDelegate*
+      CreateWindowManagerDelegate() OVERRIDE;
   virtual void OpenFeedbackPage() OVERRIDE;
   virtual void RecordUserMetricsAction(UserMetricsAction action) OVERRIDE;