LibWeb: Use StyleComputer::invalidate_rule_cache() directly everywhere

Get rid of the old, roundabout way of invalidating the rule cache by
incrementing the StyleSheetList "generation".

Instead, when something wants to invalidate the rule cache, just have it
directly invalidate the rule cache. This makes it much easier to see
what's happening anyway.

Userland/Libraries/LibWeb/CSS/CSSImportRule.cpp

@@ -85,7 +85,7 @@ void CSSImportRule::resource_did_load()
 
     m_style_sheet = move(sheet);
 
-    m_document->style_sheets().bump_generation();
+    m_document->style_computer().invalidate_rule_cache();
     m_document->invalidate_style();
 }
 

Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp

@@ -42,7 +42,7 @@ DOM::ExceptionOr<unsigned> CSSStyleSheet::insert_rule(StringView rule, unsigned
 
     if (!result.is_exception()) {
         if (m_style_sheet_list) {
-            m_style_sheet_list->bump_generation();
+            m_style_sheet_list->document().style_computer().invalidate_rule_cache();
             m_style_sheet_list->document().invalidate_style();
         }
     }
@@ -61,7 +61,7 @@ DOM::ExceptionOr<void> CSSStyleSheet::delete_rule(unsigned index)
     auto result = m_rules->remove_a_css_rule(index);
     if (!result.is_exception()) {
         if (m_style_sheet_list) {
-            m_style_sheet_list->bump_generation();
+            m_style_sheet_list->document().style_computer().invalidate_rule_cache();
             m_style_sheet_list->document().invalidate_style();
         }
     }

Userland/Libraries/LibWeb/CSS/StyleComputer.cpp

@@ -1071,7 +1071,7 @@ bool PropertyDependencyNode::has_cycles()
 
 void StyleComputer::build_rule_cache_if_needed() const
 {
-    if (m_rule_cache && m_rule_cache->generation == m_document.style_sheets().generation())
+    if (m_rule_cache)
         return;
     const_cast<StyleComputer&>(*this).build_rule_cache();
 }
@@ -1146,8 +1146,6 @@ void StyleComputer::build_rule_cache()
         dbgln("        Other: {}", m_rule_cache->other_rules.size());
         dbgln("        Total: {}", num_class_rules + num_id_rules + num_tag_name_rules + m_rule_cache->other_rules.size());
     }
-
-    m_rule_cache->generation = m_document.style_sheets().generation();
 }
 
 void StyleComputer::invalidate_rule_cache()

Userland/Libraries/LibWeb/CSS/StyleComputer.h

@@ -104,7 +104,6 @@ private:
         HashMap<FlyString, Vector<MatchingRule>> rules_by_tag_name;
         HashMap<Selector::PseudoElement, Vector<MatchingRule>> rules_by_pseudo_element;
         Vector<MatchingRule> other_rules;
-        int generation { 0 };
     };
     OwnPtr<RuleCache> m_rule_cache;
 };

Userland/Libraries/LibWeb/CSS/StyleSheetList.cpp

@@ -15,7 +15,7 @@ void StyleSheetList::add_sheet(NonnullRefPtr<CSSStyleSheet> sheet)
     sheet->set_style_sheet_list({}, this);
     m_sheets.append(move(sheet));
 
-    ++m_generation;
+    m_document.style_computer().invalidate_rule_cache();
     m_document.invalidate_style();
 }
 
@@ -24,7 +24,7 @@ void StyleSheetList::remove_sheet(CSSStyleSheet& sheet)
     sheet.set_style_sheet_list({}, nullptr);
     m_sheets.remove_first_matching([&](auto& entry) { return &*entry == &sheet; });
 
-    ++m_generation;
+    m_document.style_computer().invalidate_rule_cache();
     m_document.invalidate_style();
 }
 

Userland/Libraries/LibWeb/CSS/StyleSheetList.h

@@ -43,9 +43,6 @@ public:
 
     bool is_supported_property_index(u32) const;
 
-    int generation() const { return m_generation; }
-    void bump_generation() { ++m_generation; }
-
     DOM::Document& document() { return m_document; }
     DOM::Document const& document() const { return m_document; }