Work around rounding errors in RTL scroll type detection

This is closely related to Ied0b974 which fixed a similar, if not
the same rounding issue.

Note the following might be different depending on e.g. the
operating system. My Ubuntu+Chromium shows the following behavior:
* The RTL scroll type is correctly detected as "negative" with all
  zoom factors below and up to 100%.
* When the zoom factor is 110%, 125%, or 150% the scrollLeft value
  is not 0 but something like 0.909090876 or 0.200000002.
* It's 0 again at 175% and 200%.
* Bad at 250%. Good at 300%. Bad at 400%. And so on. No rhyme or
  reason.

The current Firefox version also ends in the "negative" branch, but
doesn't have the same rounding errors. It's always a perfect 0 in
Firefox.

This makes it look like a bug in Chrome's engine. We don't know how
old it is, but based on the information in T352169 it might be a
relatively new bug that didn't exist when this code was originally
written in 2016 (see I7c903c2).

For reference, this is what's supposed to happen here: Browsers with
the scroll type "negative" (which are apparently all current Chrome
and Firefox versions) won't allow scrollLeft to be a positive number
on an RTL page. When you scroll to the left in such browsers the
numbers get negative. The detection code tries to set the number to
+1 anyway. We expect the browser to ignore this invalid call and
still report the previous 0.

This mostly works in Chrome as well. For example, setting scrollLeft
to +100 wont set it to +100 but to … some random number between >=0
and <1, depending on the current zoom factor? o_O?

I suspect we can remove this detection code entirely, or at least
change the default to "negative". But this needs more testing with
more browsers. Let's start with this tiny fix.

Bug: T352169
Change-Id: I22cbb8881578e96165097d4fcc812baadc22d7fa

modules/ext.RevisionSlider.util.js

@@ -92,7 +92,9 @@ function determineRtlScrollType() {
 		type = 'default';
 	} else {
 		definer.scrollLeft = 1;
-		if ( definer.scrollLeft === 0 ) {
+		// T352169: While Chrome ignores the +1 above (as it should), there are strange rounding
+		// errors with many (not all) of the possible zoom factors >100%
+		if ( definer.scrollLeft < 1 ) {
 			type = 'negative';
 		}
 	}