LibWeb: Use invalidation sets to reduce style recalculation

Implements idea described in
https://docs.google.com/document/d/1vEW86DaeVs4uQzNFI5R-_xS9TcS1Cs_EUsHRSgCHGu8

Invalidation sets are used to reduce the number of elements marked for
style recalculation by collecting metadata from style rules about the
dependencies between properties that could affect an element’s style.

Currently, this optimization is only applied to style invalidation
triggered by class list mutations on an element.

Libraries/LibWeb/DOM/Node.h

@@ -14,6 +14,7 @@
 #include <AK/RefPtr.h>
 #include <AK/TypeCasts.h>
 #include <AK/Vector.h>
+#include <LibWeb/CSS/InvalidationSet.h>
 #include <LibWeb/DOM/AccessibilityTreeNode.h>
 #include <LibWeb/DOM/EventTarget.h>
 #include <LibWeb/DOM/Slottable.h>
@@ -297,6 +298,7 @@ public:
     void set_child_needs_style_update(bool b) { m_child_needs_style_update = b; }
 
     void invalidate_style(StyleInvalidationReason);
+    void invalidate_style(StyleInvalidationReason, Vector<CSS::InvalidationSet::Property> const&);
 
     void set_document(Badge<Document>, Document&);