Restart suggestions when the cursor moves.

This uses the old suggestions. It does not try to recompute
new suggestions if there are no old suggestions yet: this is
coming in a later change.
If there are no suggestions, this shows the word itself
as a suggestion.

Bug: 8084810
Change-Id: I4c2e25df0ff3673be1825f57a0c19a9d23d47a48