Pass QSize by value

QSize has 64bit (2x int), so it's not better to use a reference.
3 jobs for master in 2 minutes and 39 seconds (queued for 140 minutes and 14 seconds)
Status Name Job ID Coverage
  Test
passed build #134228

00:01:02

passed clazy #134226

00:01:14

passed qmllint #134227

00:00:22