Bug 255568 – :dir pseudo class doesn't invalidate after removing dir content attribute from document element

• Status: RESOLVED
• Resolution: FIXED
• Component: CSS

When direction is dynamically changed by setting the `dir` attribute to `rtl`, styles matching `:dir(rtl)` are applied as expected; however, if the `dir` attribute is removed, styles matching `:dir(rtl)` unexpectedly still apply.

See this reproduction: https://lit.dev/playground/#gist=b7c7e390a923d0a54b5c3211bd69a668

Expected: 
1. check the `rtl` checkbox to set document to rtl mode
2. styles matching `:dir(rtl)` apply
3. uncheck the `rtl` checkbox to set document back to default (ltr) direction
4. styles matching `:dir(rtl)` do *not* apply

Actual: 
1. check the `rtl` checkbox to set document to rtl mode
2. styles matching `:dir(rtl)` apply
3. uncheck the `rtl` checkbox to set document back to default (ltr) direction
4. styles matching `:dir(rtl)` *unexpectedly do* apply

[Radar WebKit Bug Importer]

<rdar://problem/108480507>

[Ryosuke Niwa]

Pull request: https://github.com/WebKit/WebKit/pull/13134

[EWS]

Committed 263357@main (a3084fe071c6): <https://commits.webkit.org/263357@main>

Reviewed commits have been landed. Closing PR #13134 and removing active labels.