Intent to unship: SVGPathSeg APIs

[Boris Chiou]

Hi,

As of Firefox 97, we intend to remove the following legacy SVGPathSeg related APIs on all platforms:

1. SVGAnimatedPathData
2. SVGPathSeg
3. SVGPathSegList
4. SVGPathElement::getPathSegAtLength()

The SVG spec removed these APIs already (spec link), and maintaining these legacy APIs has some overhead after we made d property as a presentation attribute. Besides, we still can use d property to get its computed style so we still have ability to know the animated values. The current WPT also use d property as the way to verify SVG animations. So this should be safe to obsolete these APIs.

Status in other browsers is:
1. Blink removed these APIs 5 years ago.
2. WebKit still have these APIs.

Bug to remove: https://bugzilla.mozilla.org/show_bug.cgi?id=1388931

Thanks,
Boris