[Icon] Change default fontSize name

[oliviertassinari]

Deprecation

Few people should be affected by this change as it focuses on the default value. Most people don't specify the default value, and if you have specified a wrong value, it will only warn, the output should be the same.

-<Icon size="default" />
+<Icon size="medium" />
-<SvgIcon size="default" />
+<SvgIcon size="medium" />

Why? It's for consistency:
https://github.com/mui-org/material-ui/blob/d1a7d76db79b2f1f03068c7c3bc0c9f28a7c5a64/packages/material-ui/src/Button/Button.js#L292
https://github.com/mui-org/material-ui/blob/d1a7d76db79b2f1f03068c7c3bc0c9f28a7c5a64/packages/material-ui/src/TableCell/TableCell.js#L203

[mui-pr-bot]

Details of bundle changes.

Comparing: d1a7d76...7263762

bundle	parsed diff	gzip diff	prev parsed	current parsed	prev gzip	current gzip
@material-ui/core	-0.00%	-0.01%	352,929	352,927	90,642	90,633
@material-ui/core/Paper	0.00%	0.00%	68,626	68,626	19,974	19,974
@material-ui/core/Paper.esm	0.00%	0.00%	62,358	62,358	19,075	19,075
@material-ui/core/Popper	0.00%	-0.01%	30,460	30,460	10,528	10,527
@material-ui/core/styles/createMuiTheme	0.00%	0.00%	17,384	17,384	5,726	5,726
@material-ui/core/useMediaQuery	0.00%	0.00%	2,469	2,469	1,037	1,037
@material-ui/lab	-0.00%	0.00%	152,181	152,180	44,533	44,535
@material-ui/styles	0.00%	0.00%	53,837	53,837	15,613	15,613
@material-ui/system	0.00%	0.00%	17,138	17,138	4,520	4,520
Button	0.00%	0.00%	90,918	90,918	26,970	26,970
Modal	0.00%	-0.00%	84,712	84,712	25,262	25,261
colorManipulator	0.00%	0.00%	3,232	3,232	1,300	1,300
docs.landing	0.00%	0.00%	51,843	51,843	11,349	11,349
docs.main	0.00%	0.00%	647,762	647,773	201,135	201,138
packages/material-ui/build/umd/material-ui.production.min.js	-0.00%	0.00%	301,958	301,956	83,730	83,730

Generated by 🚫 dangerJS against 7263762

[eps1lon]

Can't we just alias default to medium for now and add a deprecation message in the prop types validator?

[oliviertassinari]

@eps1lon OK

[oliviertassinari]

I'm closing for the moment. I will come back to it later, probably in 4-6 months to prepare v5.