Intent to deprecate: MathML scriptminsize and scriptsizemultiplier attributes

[Frédéric Wang]

In bug 1548471, I intend to deprecate the MathML scriptminsize and
scriptsizemultiplier attributes. These are used to let people provide
custom style for a minimal font-size when doing scriptlevel changes or
a scale factor to apply to font-size at each scriptlevel change.

The MathML Refresh CG agreed to remove these attributes from MathML
Core. These attributes don't seem to be used by authoring tools and
there does not seem to be any plan to implement them in other browsers.
Their effect might still be interesting, but the use cases would likely
be better achieve by other means (e.g. making CSS math-depth a float,
using OpenType MATH script-related scales, limiting math-depth automatic
increment to small values, not putting font-family: math on deep nodes,
relying on font.minimum-size.x-math etc). For now, the default
scriptminsize="8pt" would still apply but won't be customizable.

The plan is to setup telemetry & deprecation warning and then analyze
later whether we can remove them.

Spec: https://www.w3.org/Math/draft-spec/chapter3.html#presm.mstyle.attrs
Decision:
https://lists.w3.org/Archives/Public/public-mathml4/2019Apr/0022.html
MathML Core analysis: https://github.com/mathml-refresh/mathml/issues/55

--
Frédéric Wang