Remove the objectSize helper function

[Snuffleupagus]

Given that Maps are used a lot more these days, this helper function is now used very sparingly and inlining the necessary code seems reasonable.

Note: Once this proposal makes it into Firefox, we should be able to simplify all Object.keys(...).length call-sites.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.85%. Comparing base (fe0b880) to head (675e921).

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #21624   +/-   ##
=======================================
  Coverage   89.85%   89.85%           
=======================================
  Files         263      263           
  Lines       66809    66808    -1     
=======================================
+ Hits        60029    60031    +2     
+ Misses       6780     6777    -3     

Flag	Coverage Δ
browsertest	66.53% <100.00%> (+<0.01%)	⬆️
fonttest	9.05% <0.00%> (+<0.01%)	⬆️
integrationtest	69.26% <100.00%> (+<0.01%)	⬆️
unittest	57.52% <100.00%> (+<0.01%)	⬆️
unittestcli	56.49% <100.00%> (+0.01%)	⬆️

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[calixteman]

LGTM. Thank you.

[timvandermeij]

Thanks!