[css-inline] Baseline position may not be interoperable

[kojiishi]

From @dbaron's comment on Apr 21st, even when line-height is set to a value other than normal and the used line height is consistent, the baseline position may not be consistent in some browsers.

CSS2 does not define this, and I'm filing this not to loose. Do we want to work on this?

[litherum]

Baseline position is dependent on font metrics, which are different between browsers and different between the same browser on different platforms.

[frivoal]

This used to be undefined, but has now been sorted out.

• diagram of possibilities: https://lists.w3.org/Archives/Public/www-archive/2017Apr/att-0008/IMG_20170421_173959.jpg
• test results:
  • [css21][css-inline] height of inline box with line-height not normal #1797 (excludes black behavior in diagram)
  • [css21][css-inline] Position of the baseline inline-level boxes with non normal line-height #1801 (clarifies we get the blue behavior, not the red one)
• Resolution: https://lists.w3.org/Archives/Public/www-style/2017Dec/0007.html
• commit: a3c7617