Fix flicker when tapping quickly on dock divider

- Only add preserved surface to removal list when the new surface is shown

- When surface mode change again before the previous preserved surface is
  removed, don't do nothing, instead, destroy the current surface which is
  of wrong size.

  bug: 26545679

Change-Id: Ifd548a0fa9ccdcbc9609ca38bb701cc7256cc6e1
(cherry picked from commit ec63381f)