HighlightInheritance: compat stroke properties valid_for_highlight

‘-webkit-text-fill-color’ is valid_for_highlight, but we forgot to
mark ‘-webkit-text-stroke-color’ and ‘-webkit-text-stroke-width’ as
valid_for_highlight too. They are only valid_for_highlight_legacy
at the moment.

Whether all three should be applicable is pending a spec issue [1],
but HighlightInheritance is not stable yet anyway, and enabling them
in this patch unblocks bumping HighlightInheritance to experimental.

[1] https://github.com/w3c/csswg-drafts/issues/7580

Bug: 1024156
Change-Id: Ifcd121800ffe9d0cae0b7984f98cf9bf1c83f002
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4060396
Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org>
Commit-Queue: Delan Azabani <dazabani@igalia.com>
Cr-Commit-Position: refs/heads/main@{#1078054}
diff --git a/css/css-pseudo/highlight-styling-003-ref.html b/css/css-pseudo/highlight-styling-003-ref.html
new file mode 100644
index 0000000..d6db9cf
--- /dev/null
+++ b/css/css-pseudo/highlight-styling-003-ref.html
@@ -0,0 +1,16 @@
+<!doctype html>
+<meta charset="utf-8">
+<link rel="author" title="Delan Azabani" href="mailto:dazabani@igalia.com">
+<link rel="stylesheet" href="support/highlights.css">
+<style>
+    main {
+        font-size: 7em;
+        margin: 0.5em;
+        color: white;
+        -webkit-text-fill-color: yellow;
+        -webkit-text-stroke-color: green;
+        -webkit-text-stroke-width: 4px;
+    }
+</style>
+<p>Test passes if the text below is yellow with a green outline.
+<main class="highlight_reftest">quick</main>
diff --git a/css/css-pseudo/highlight-styling-003.tentative.html b/css/css-pseudo/highlight-styling-003.tentative.html
new file mode 100644
index 0000000..70d3dc6
--- /dev/null
+++ b/css/css-pseudo/highlight-styling-003.tentative.html
@@ -0,0 +1,25 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>CSS Pseudo-Elements Test: highlight styling: compat stroke/fill properties</title>
+<link rel="author" title="Delan Azabani" href="mailto:dazabani@igalia.com">
+<link rel="help" href="https://drafts.csswg.org/css-pseudo-4/#highlight-styling">
+<link rel="help" href="https://compat.spec.whatwg.org/#text-fill-and-stroking">
+<link rel="match" href="highlight-styling-003-ref.html">
+<meta name="assert" value="This test verifies that the compat stroke/fill properties are applicable to ::selection.">
+<script src="support/selections.js"></script>
+<link rel="stylesheet" href="support/highlights.css">
+<style>
+    main {
+        font-size: 7em;
+        margin: 0.5em;
+    }
+    main::selection {
+        color: white;
+        -webkit-text-fill-color: yellow;
+        -webkit-text-stroke-color: green;
+        -webkit-text-stroke-width: 4px;
+    }
+</style>
+<p>Test passes if the text below is yellow with a green outline.
+<main class="highlight_reftest">quick</main>
+<script>selectNodeContents(document.querySelector("main"));</script>