Libraries: Create top level directory for libraries.

Things were getting a little crowded in the project root, so this patch
moves the Lib*/ directories into Libraries/.

Libraries/LibHTML/Layout/LayoutNode.h

@@ -0,0 +1,58 @@
+#pragma once
+
+#include <AK/NonnullRefPtr.h>
+#include <AK/Vector.h>
+#include <LibHTML/Layout/ComputedStyle.h>
+#include <LibHTML/TreeNode.h>
+#include <SharedGraphics/Rect.h>
+
+class Node;
+class LayoutBlock;
+class StyledNode;
+
+class LayoutNode : public TreeNode<LayoutNode> {
+public:
+    virtual ~LayoutNode();
+
+    const Rect& rect() const { return m_rect; }
+    Rect& rect() { return m_rect; }
+    void set_rect(const Rect& rect) { m_rect = rect; }
+
+    ComputedStyle& style() { return m_style; }
+    const ComputedStyle& style() const { return m_style; }
+
+    bool is_anonymous() const { return !m_node; }
+    const Node* node() const { return m_node; }
+
+    template<typename Callback>
+    inline void for_each_child(Callback callback) const
+    {
+        for (auto* node = first_child(); node; node = node->next_sibling())
+            callback(*node);
+    }
+
+    template<typename Callback>
+    inline void for_each_child(Callback callback)
+    {
+        for (auto* node = first_child(); node; node = node->next_sibling())
+            callback(*node);
+    }
+
+    virtual const char* class_name() const { return "LayoutNode"; }
+    virtual bool is_text() const { return false; }
+    virtual bool is_block() const { return false; }
+
+    virtual void layout();
+
+    const LayoutBlock* containing_block() const;
+
+protected:
+    explicit LayoutNode(const Node*, const StyledNode&);
+
+private:
+    const Node* m_node { nullptr };
+    NonnullRefPtr<StyledNode> m_styled_node;
+
+    ComputedStyle m_style;
+    Rect m_rect;
+};