LibHTML: Anonymous blocks *should* inherit some properties

Okay, I got that a bit wrong. Here's what CSS 2.1 says:

"The properties of anonymous boxes are inherited from the enclosing
non-anonymous box. Non-inherited properties have their initial value."

This patch implements a better behavior by only copying the inherited
properties from the parent style.

Libraries/LibHTML/CSS/StyleResolver.h

@@ -22,6 +22,8 @@ public:
 
     NonnullRefPtrVector<StyleRule> collect_matching_rules(const Element&) const;
 
+    static bool is_inherited_property(const StringView&);
+
 private:
     template<typename Callback>
     void for_each_stylesheet(Callback) const;