bug#45898: 27.1; wedged in redisplay again

[Stefan Monnier]

>> Unsuprisingly so: none of `C-n/C-p/C-v/...` involve font-lock or
>> jit-lock either during their operation or during the
>> subsequent redisplay phase in the current code: the one-line is all
>> fontified once and for all when you open the file and after that
>> font-lock is not involved any more (until you make an edit, that is).
>
> That's only true if max-redisplay-ticks is zero.

Why would that make a difference?  When I try `master` with this set to
100000, the file still shows up with font-locking, so apparently it's
been fully font-locked despite `max-redisplay-ticks` and after that
font-locking (and syntax-propertize) won't make any difference any more
(until the buffer is edited) since they're already done.
[ Of course font-locking (and syntax-propertize) still do have an
  effect in that the text-properties they applied can impact the time it
  takes for the redisplay to do its job; so by "won't make any difference"
  I mean that 0-cycles will be spent running font-lock of
  syntax-propertize code.  ]


        Stefan