Fix Chromium issue 468928416: implement text-decoration-inset in Blink

[hjanuschka]

Chromium Issue

https://issues.chromium.org/issues/468928416

Description

Implemented text-decoration-inset in Blink, allowing authors to offset the underline / overline / line-through decoration from its default position on the text baseline.

CLs involved

1. https://chromium-review.googlesource.com/c/chromium/src/+/7993418
   Add text-decoration-inset style support in Blink (parsing, computed style, and AppliedTextDecoration plumbing behind the CSSTextDecorationInset runtime flag).
2. https://chromium-review.googlesource.com/c/chromium/src/+/7748204
   Implement text-decoration-inset painting in Blink, including inline fragment boundary handling for sliced/cloned boxes and SVG fragments; removes WPT expectations for the now-supported rendering cases.
3. https://chromium-review.googlesource.com/c/chromium/src/+/8128018
   Triage remaining text-decoration-inset test failures.

Demo

https://static.januschka.com/i-468928416/

Status

All 3 CLs merged.

[hjanuschka]

gosh, on hold, i'll prepare the i2s, flag is still experimental!! sorry