LibWeb: Apply style rules in order of specificity (kinda)

We now sort the matched rules by the specificity of the first selector
in them. This is not perfect, since a rule can have multiple selectors,
but it is a nice chin-related progression on ACID2. :^)

Libraries/LibWeb/CSS/StyleResolver.cpp

@@ -24,6 +24,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <AK/QuickSort.h>
 #include <LibWeb/CSS/SelectorEngine.h>
 #include <LibWeb/CSS/StyleResolver.h>
 #include <LibWeb/CSS/StyleSheet.h>
@@ -439,6 +440,13 @@ NonnullRefPtr<StyleProperties> StyleResolver::resolve_style(const Element& eleme
  element.apply_presentational_hints(*style);
 
  auto matching_rules = collect_matching_rules(element);
+
+ // FIXME: We need to look at the specificity of the matching *selector*, not just the matched *rule*!
+ // FIXME: It's really awkward that NonnullRefPtrVector cannot be quick_sort()'ed
+ quick_sort(reinterpret_cast<Vector<NonnullRefPtr<StyleRule>>&>(matching_rules), [&](auto& a, auto& b) {
+ return a->selectors().first().specificity() < b->selectors().first().specificity();
+ });
+
  for (auto& rule : matching_rules) {
  for (auto& property : rule.declaration().properties()) {
  set_property_expanding_shorthands(style, property.property_id, property.value);

Libraries/LibWeb/CSS/StyleRule.h

@@ -33,6 +33,9 @@
 namespace Web {
 
 class StyleRule : public RefCounted<StyleRule> {
+ AK_MAKE_NONCOPYABLE(StyleRule);
+ AK_MAKE_NONMOVABLE(StyleRule);
+
 public:
  static NonnullRefPtr<StyleRule> create(Vector<Selector>&& selectors, NonnullRefPtr<StyleDeclaration>&& declaration)
  {