[ScrollbarSize] Convert to function component

[joshwooding]

• I have followed (at least) the PR section of the contributing guide.

Was an easy one to do.

[mui-pr-bot]

@material-ui/core: parsed: -0.11% 😍, gzip: -0.03% 😍

Details of bundle changes.

Comparing: bd7f1e7...8454fe0

bundle	parsed diff	gzip diff	prev parsed	current parsed	prev gzip	current gzip
@material-ui/core	-0.11%	-0.03%	348,521	348,150	89,908	89,882
@material-ui/core/Paper	0.00%	0.00%	68,404	68,404	20,054	20,054
@material-ui/core/Paper.esm	0.00%	-0.01%	60,735	60,735	18,788	18,787
@material-ui/core/Popper	0.00%	-0.01%	34,930	34,930	11,918	11,917
@material-ui/core/styles/createMuiTheme	0.00%	0.00%	17,877	17,877	5,962	5,962
@material-ui/core/useMediaQuery	0.00%	0.00%	2,463	2,463	1,045	1,045
@material-ui/lab	0.00%	-0.00%	148,083	148,083	43,916	43,915
@material-ui/styles	0.00%	-0.03%	53,143	53,143	15,446	15,442
@material-ui/system	0.00%	0.00%	17,132	17,132	4,519	4,519
Button	0.00%	+0.01% 🔺	88,669	88,669	26,420	26,422
Modal	0.00%	0.00%	82,688	82,688	24,800	24,800
colorManipulator	0.00%	0.00%	3,745	3,745	1,537	1,537
docs.landing	0.00%	0.00%	49,820	49,820	10,807	10,807
docs.main	0.00%	0.00%	644,483	644,483	200,635	200,635
packages/material-ui/build/umd/material-ui.production.min.js	-0.12%	-0.00%	297,102	296,736	82,867	82,864

Generated by 🚫 dangerJS against 8454fe0

[joshwooding]

@material-ui/core: parsed: -0.09% 😍, gzip: 0.00% 😍

Details of bundle changes.
Generated by 🚫 dangerJS against 3c04240

Gotta love the 0% change 😄 and removing EventListener makes it -0.02% 😛

[oliviertassinari]

@joshwooding I don't keep track of the progres. Do you have an estimation of the % of migrated components?

[eps1lon]

@oliviertassinari #15231

[oliviertassinari]

@eps1lon Right, that the components left to be migrated. I was wondering about the overall progress, 60%?

[eps1lon]

There are around 110 components in core+lab. It's probably closer to 75-80%.