Bug 1855181 [wpt PR 42159] - [css-properties-values-api] Make empty universal custom props valid, a=testonly

Automatic update from web-platform-tests
[css-properties-values-api] Make empty universal custom props valid

In CustomProperty::ApplyValue, we parse the specified token sequence
(in this case an empty sequence), against the registered grammar
(in this case the universal syntax), and ultimately we call
CSSVariableParser::ParseVariableReferenceValue, to "parse" this
empty token sequence. ParseVariableReferenceValue had an incorrect
check on empty ranges - likely a remnant of the old spec, which did
not allow empty values.

Fixed: 1485804
Change-Id: I13ba8d9196c50a5a74c5991e2fec4c961b6a0c28
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4890262
Reviewed-by: Steinar H Gunderson <sesse@chromium.org>
Commit-Queue: Anders Hartvoll Ruud <andruud@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1201429}

--

wpt-commits: b956706efa6bc6a637b4de8bbc001da4fe9fef9c
wpt-pr: 42159

testing/web-platform/tests/css/css-properties-values-api/var-reference-registered-properties.html

@@ -221,4 +221,21 @@ test_using_invalid_fallback('<length>', 'red');
 test_using_invalid_fallback('<length> | none', 'nolength');
 test_using_invalid_fallback('<color>', 'var(--length-1)');
 
+test(function(t){
+    CSS.registerProperty({
+        name: '--registered-universal-no-initial',
+        syntax: '*',
+        inherits: false
+    });
+    t.add_cleanup(() => {
+        element.style = '';
+    });
+    element.style = [
+        '--registered-universal-no-initial:;',
+        'background-color: var(--registered-universal-no-initial) green',
+    ].join(';');
+    let computedStyle = getComputedStyle(element);
+    assert_equals(computedStyle.getPropertyValue('background-color'), 'rgb(0, 128, 0)');
+}, 'Empty universal custom property can be substituted with var()');
+
 </script>