shutdown:update display_info.c

1.add GtkWidget* in draw_background_by_rect

2.add TODO to a bug:
   a.Now update_bg is called by root window filter
      But update_bg use the _DDE_BACKGROUND_WINDOW to cairo
      And the _DDE_BACKGROUND_WINDOW is update by the Display DBus
      signal "PrimaryChanged"

      ---so two signal has the order
      ---root window changed && "PrimaryChanged"

    solve:update_bg must called bt "PrimaryChanged" signal
          But we will change the 窗口管理器.
          so after we change it, then, all signal will be root window filter

3.the bug will cause that:
   if you connect two monitors,and they are in extend mode.
   And you execute dde-shutdown,
   then you put out one of the monitor,
   And the background will be right.
   But if you put in the one,
   the background maybe draw in only one monitor, not in all monitors.

Change-Id: I1c1ff51498a4cbef6939b951bacd9eb625437301