Fix animation of stop-color on <stop>

[Ahmad Saleem]

Hi Team,

While going through Blink's commit, I came across another failing WPT test case:

Blink Commit: https://chromium.googlesource.com/chromium/src.git/+/176379b6e15a3a0ae8b65bb493691ffd00ed3767

WPT link: https://wpt.fyi/results/svg/animations/animate-stop-currentcolor.html?label=master&label=experimental&aligned&q=animate-stop-currentcolor.html

WPT Test link: http://wpt.live/svg/animations/animate-stop-currentcolor.html

It might be duplicate of bug 95083 (especially [2] bullet point).

Just wanted to raise so we can track but if it is duplicate, we can mark this as well. Why I am not doing it straight away because the test case in other bug is working same as Chrome Canary 115 and Safari 16.4.1.

Thanks!

[Radar WebKit Bug Importer]

<rdar://problem/109823555>

[Ahmad Saleem]

Similar looking function (SVGStopElement::stopColorIncludingOpacity()):

https://searchfox.org/wubkat/source/Source/WebCore/svg/SVGStopElement.cpp#87

if (!renderer())
        return Color::transparentBlack;

    auto& style = renderer()->style();
    auto& svgStyle = style.svgStyle();
    auto stopColor = style.colorResolvingCurrentColor(svgStyle.stopColor());

    return stopColor.colorWithAlphaMultipliedBy(svgStyle.stopOpacity());

[Rob Buis]

Pull request: https://github.com/WebKit/WebKit/pull/19112