Prevent deleted count from being wrongly decremented

* This could happen if a refresh() happens before an undo(); the
  result could easily be crashes or other bad behavior, as
  sDeletedCount drops below zero
* I suspect this will fix a number of bugs, but let's let it soak
  a bit, perhaps, before considering them closed

Bug: 6249265
Change-Id: I37c612ceb4d22fc57f1daa96aab316ff8405bef6
1 file changed