Add test to make sure CSSFontPaletteValuesRule's attributes are readonly

https://bugs.webkit.org/show_bug.cgi?id=230791
<rdar://problem/83530165>

Reviewed by Simon Fraser.

The spec enforces this in w3c/csswg-drafts@9ddf938. This is already the case in WebKit.

This is being upstreamed in web-platform-tests/wpt#30964.

* web-platform-tests/css/css-fonts/parsing/font-palette-values-invalid.html:

Canonical link: https://commits.webkit.org/242202@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@283154 268f45cc-cd09-0410-ab3c-d52691b4dbfc

LayoutTests/imported/w3c/ChangeLog

@@ -1,3 +1,17 @@
+2021-09-27  Myles C. Maxfield  <mmaxfield@apple.com>
+
+        Add test to make sure CSSFontPaletteValuesRule's attributes are readonly
+        https://bugs.webkit.org/show_bug.cgi?id=230791
+        <rdar://problem/83530165>
+
+        Reviewed by Simon Fraser.
+
+        The spec enforces this in w3c/csswg-drafts@9ddf938. This is already the case in WebKit.
+
+        This is being upstreamed in https://github.com/web-platform-tests/wpt/pull/30964.
+
+        * web-platform-tests/css/css-fonts/parsing/font-palette-values-invalid.html:
+
 2021-09-27  Myles C. Maxfield  <mmaxfield@apple.com>
 
         Add support for CSSFontPaletteValuesRule.name

LayoutTests/imported/w3c/web-platform-tests/css/css-fonts/parsing/font-palette-values-invalid.html

@@ -115,6 +115,20 @@
     let rule = rules[0];
     assert_equals(text.indexOf("font-family"), -1);
     assert_equals(rule.fontFamily, "");
+    rule.fontFamily = "SomeFontFamily";
+    assert_equals(rule.fontFamily, "");
+    assert_equals(rule.basePalette, "");
+    rule.basePalette = "7";
+    assert_equals(rule.basePalette, "");
+    assert_throws_js(TypeError, function() {
+        rule.clear();
+    });
+    assert_throws_js(TypeError, function() {
+        rule.delete(4);
+    });
+    assert_throws_js(TypeError, function() {
+        rule.set(4, "0 #123");
+    });
 });
 
 test(function() {