LibWeb: Invalidate stylesheet owners when disabled state changes

Toggling CSSStyleSheet::disabled previously cleared the cached media
match bits and reloaded fonts, but never informed the owning documents
or shadow roots that style resolution was now stale. Worse, the IDL
binding for the disabled attribute dispatches through a non-virtual
setter on StyleSheet, so any override on CSSStyleSheet was bypassed
entirely.

Make set_disabled() virtual so the CSSStyleSheet override actually runs,
snapshot the pre-mutation shadow-root stylesheet effects before flipping
the flag, and hand them to invalidate_owners() so a disable that strips
the last host-reaching rule still tears down host-side style correctly.

Libraries/LibWeb/CSS/CSSStyleSheet.cpp

@@ -384,6 +384,7 @@ void CSSStyleSheet::set_disabled(bool disabled)
     if (this->disabled() == disabled)
         return;
 
+    auto previous_sheet_effects = determine_shadow_root_stylesheet_effects(*this);
     auto document = owning_document();
     // When a stylesheet is disabled we stop evaluating its media queries, so both the cached top-level match bit
     // and the MediaList's internal state can go stale across viewport changes. Clear the cache for both
@@ -401,6 +402,8 @@ void CSSStyleSheet::set_disabled(bool disabled)
     } else if (document) {
         document->font_computer().unload_fonts_from_sheet(*this);
     }
+
+    invalidate_owners(DOM::StyleInvalidationReason::StyleSheetDisabledStateChange, &previous_sheet_effects);
 }
 
 void CSSStyleSheet::for_each_owning_style_scope(Function<void(StyleScope&)> const& callback) const

Libraries/LibWeb/CSS/CSSStyleSheet.h

@@ -95,7 +95,7 @@ public:
     void remove_owning_document_or_shadow_root(DOM::Node& document_or_shadow_root);
     void invalidate_owners(DOM::StyleInvalidationReason, ShadowRootStylesheetEffects const* previous_sheet_effects = nullptr);
     GC::Ptr<DOM::Document> owning_document() const;
-    void set_disabled(bool);
+    virtual void set_disabled(bool) override;
     void for_each_owning_style_scope(Function<void(StyleScope&)> const&) const;
 
     Optional<FlyString> default_namespace() const;

Libraries/LibWeb/CSS/StyleSheet.h

@@ -54,7 +54,7 @@ public:
     void set_origin_clean(bool origin_clean) { m_origin_clean = origin_clean; }
 
     bool disabled() const { return m_disabled; }
-    void set_disabled(bool disabled) { m_disabled = disabled; }
+    virtual void set_disabled(bool disabled) { m_disabled = disabled; }
 
     CSSStyleSheet* parent_style_sheet() { return m_parent_style_sheet; }
     void set_parent_css_style_sheet(CSSStyleSheet*);

Tests/LibWeb/Text/expected/css/stylesheet-disabled-toggle-invalidation.txt

@@ -0,0 +1,3 @@
+before disable: rgb(255, 0, 0)
+after disable: rgb(0, 0, 0)
+after re-enable: rgb(255, 0, 0)

Tests/LibWeb/Text/expected/wpt-import/css/cssom/CSSStyleSheet-constructable.txt

@@ -2,8 +2,8 @@ Harness status: OK
 
 Found 32 tests
 
-27 Pass
-5 Fail
+29 Pass
+3 Fail
 Pass	document.adoptedStyleSheets should initially have length 0.
 Pass	new CSSStyleSheet produces empty CSSStyleSheet
 Pass	title can be set in the CSSStyleSheet constructor
@@ -21,8 +21,8 @@ Pass	Adding non-constructed stylesheet to AdoptedStyleSheets is not allowed when
 Pass	Adding non-constructed stylesheet to AdoptedStyleSheets is not allowed when the owner document of the stylesheet and the AdoptedStyleSheets are in different document trees
 Pass	CSSStyleSheet.replaceSync replaces stylesheet text synchronously
 Pass	CSSStyleSheet.replaceSync correctly updates the style of its adopters synchronously
-Fail	Adopted sheets are ordered after non-adopted sheets in the shadow root
-Fail	Adopted sheets are ordered after non-adopted sheets in the document
+Pass	Adopted sheets are ordered after non-adopted sheets in the shadow root
+Pass	Adopted sheets are ordered after non-adopted sheets in the document
 Pass	Inserting an @import rule through insertRule on a constructed stylesheet throws an exception
 Fail	CSSStyleSheet.replaceSync should not trigger any loads from @import rules
 Pass	CSSStyleSheet.replace allows, but ignores, import rule inside

Tests/LibWeb/Text/input/css/stylesheet-disabled-toggle-invalidation.html

@@ -0,0 +1,40 @@
+<!DOCTYPE html>
+<script src="../include.js"></script>
+<div id="target" class="foo">target</div>
+<div>bystander 1</div>
+<div>bystander 2</div>
+<div>bystander 3</div>
+<script>
+    function settleAndReset(triggerElement) {
+        getComputedStyle(triggerElement).color;
+        getComputedStyle(triggerElement).color;
+        internals.resetStyleInvalidationCounters();
+    }
+
+    function addBystanders(parent, count) {
+        for (let i = 0; i < count; ++i) {
+            const bystander = document.createElement("div");
+            bystander.textContent = `bystander ${i + 4}`;
+            parent.appendChild(bystander);
+        }
+    }
+
+    test(() => {
+        const target = document.getElementById("target");
+        addBystanders(document.body, 25);
+
+        const sheet = new CSSStyleSheet();
+        sheet.replaceSync(".foo { color: rgb(255, 0, 0); }");
+        document.adoptedStyleSheets = [sheet];
+
+        println(`before disable: ${getComputedStyle(target).color}`);
+
+        settleAndReset(target);
+        sheet.disabled = true;
+        println(`after disable: ${getComputedStyle(target).color}`);
+
+        settleAndReset(target);
+        sheet.disabled = false;
+        println(`after re-enable: ${getComputedStyle(target).color}`);
+    });
+</script>