Avoid zooming during fast two-finger panning

[calixteman]

Round scale updates and carry rounding error. Filter span changes consistent with staggered touch samples.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.19%. Comparing base (3cb74c4) to head (e05ab5e).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #21807   +/-   ##
=======================================
  Coverage   90.18%   90.19%           
=======================================
  Files         264      264           
  Lines       67332    67350   +18     
=======================================
+ Hits        60724    60746   +22     
+ Misses       6608     6604    -4     

Flag	Coverage Δ
browsertest	66.33% <0.00%> (+0.01%)	⬆️
fonttest	8.91% <ø> (ø)
integrationtest	69.39% <82.60%> (+0.01%)	⬆️
unittest	58.35% <100.00%> (-0.01%)	⬇️
unittestcli	56.94% <100.00%> (+0.03%)	⬆️

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[timvandermeij]

Looks good to me, with the comment addressed. Thanks!