LibHTML+Browser: Support scrolling to anchor with <a href="#foo">

This patch implements basic support for <a href="#foo"> fragment links.

To figure out where we actually want to scroll to, we have to do
something different based on the layout node's box type. So if it's a
regular LayoutBox we can just use the LayoutBox::position().

However, if it's an inline layout node, we use the position of the
first line box fragment in the containing block contributed by this
layout node or one of its descendants.

Libraries/LibHTML/Layout/LayoutNode.h

@@ -80,9 +80,6 @@ public:
 
     virtual void set_needs_display();
 
-    template<typename Callback>
-    void for_each_fragment_of_this(Callback);
-
     bool children_are_inline() const { return m_children_are_inline; }
     void set_children_are_inline(bool value) { m_children_are_inline = value; }
 
@@ -104,6 +101,8 @@ public:
     template<typename T>
     T* first_ancestor_of_type();
 
+    Point box_type_agnostic_position() const;
+
 protected:
     explicit LayoutNode(const Node*);