This improves LOK dialog opening time considerably.

libreofficekit/tilebench results:

Before:
profile run:
  initialization - 346.5185(ms)
  load document - 2162.5881(ms)
  open dialog - 7077.8980(ms)
  wait for dialog - 52.7742(ms)
  render dialog - 256.9597(ms)
  post close dialog - 523.7811(ms)
  destroy document - 58.3723(ms)
Total: 10.4789(s)

After:
profile run:
  initialization - 336.5867(ms)
  load document - 2155.5481(ms)
  open dialog - 1151.4130(ms)
  wait for dialog - 51.5332(ms)
  render dialog - 260.3197(ms)
  post close dialog - 519.8729(ms)
  destroy document - 56.7322(ms)
Total: 4.5320(s)

Change-Id: I6345aca33c5881aba33c8a5f74765b99fe098711
Reviewed-on: https://gerrit.libreoffice.org/57561
Tested-by: Jenkins
Reviewed-by: pranavk <pranavk@collabora.co.uk>