LibHTML: Refactor to go from DOM -> styled tree -> layout tree.

Frame::layout() drives everything now, it takes the DOM contained in the
frame and puts it through the tree transformations.

LibHTML/DOM/Text.cpp

@@ -10,8 +10,3 @@ Text::Text(const String& data)
 Text::~Text()
 {
 }
-
-RefPtr<LayoutNode> Text::create_layout_node()
-{
-    return adopt(*new LayoutText(*this));
-}