[Gap Decorations] Introduce CSS Value Repeat class
This CL introduces a data structure for parsing gap decoration
properties such as color, style and width. It begins by introducing a
new CSSValue (CSSRepeatValue) that will be used to represent the
repeater notations for these properties and any future properties that
use the same grammar.
This CL also adds a VirtualTestSuite, css-gap-decoration, to exercise
code added for the feature.
Draft spec: https://kbabbitt.github.io/css-gap-decorations/#column-row-rule-color
Bug: 357648037
Change-Id: I814bec63e289d2e670dea56248a0e8b734efcad2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5856542
Reviewed-by: Kevin Babbitt kbabbitt@microsoft.com
Commit-Queue: Sam Davis Omekara samomekarajr@microsoft.com
Reviewed-by: Alison Maher almaher@microsoft.com
Cr-Commit-Position: refs/heads/main@{#1364469}