text-align: match-parent on root handles direction incorrectly

https://bugs.webkit.org/show_bug.cgi?id=241164

Reviewed by Myles C. Maxfield.

The spec says the initial containing block's direction should be used when the element has no parent.

Regarding the computed value, Chrome & Firefox computes to `start` for this case.
This may change in w3c/csswg-drafts#6542 to `left`/`right`.

Test: imported/w3c/web-platform-tests/css/css-text/text-align/text-align-match-parent-root-rtl.html

* LayoutTests/TestExpectations:
* Source/WebCore/style/StyleBuilderConverter.h:
(WebCore::Style::BuilderConverter::convertTextAlign):

Canonical link: https://commits.webkit.org/251211@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@295120 268f45cc-cd09-0410-ab3c-d52691b4dbfc

LayoutTests/TestExpectations

@@ -2645,7 +2645,6 @@ webkit.org/b/183258 imported/w3c/web-platform-tests/css/css-text/text-align/text
 webkit.org/b/183258 imported/w3c/web-platform-tests/css/css-text/text-align/text-align-last-010.html [ ImageOnlyFailure ]
 webkit.org/b/183258 imported/w3c/web-platform-tests/css/css-text/text-align/text-align-last-011.html [ ImageOnlyFailure ]
 webkit.org/b/214290 imported/w3c/web-platform-tests/css/css-text/text-align/text-align-last-wins-001.html [ ImageOnlyFailure ]
-webkit.org/b/241164 imported/w3c/web-platform-tests/css/css-text/text-align/text-align-match-parent-root-rtl.html [ ImageOnlyFailure ]
 webkit.org/b/214290 imported/w3c/web-platform-tests/css/css-text/text-encoding/shaping-join-003.html [ ImageOnlyFailure ]
 webkit.org/b/214290 imported/w3c/web-platform-tests/css/css-text/text-encoding/shaping-tatweel-002.html [ ImageOnlyFailure ]
 webkit.org/b/214290 imported/w3c/web-platform-tests/css/css-text/text-encoding/shaping-tatweel-003.html [ ImageOnlyFailure ]

Source/WebCore/style/StyleBuilderConverter.h

@@ -614,6 +614,10 @@ inline TextAlignMode BuilderConverter::convertTextAlign(BuilderState& builderSta
     if (primitiveValue.valueID() != CSSValueWebkitMatchParent && primitiveValue.valueID() != CSSValueMatchParent)
         return primitiveValue;
 
+    auto* element = builderState.element();
+    if (element && element == builderState.document().documentElement())
+        return TextAlignMode::Start;
+
     auto& parentStyle = builderState.parentStyle();
     if (parentStyle.textAlign() == TextAlignMode::Start)
         return parentStyle.isLeftToRightDirection() ? TextAlignMode::Left : TextAlignMode::Right;