LibHTML: Have Document track its hovered Node

This gets set from HtmlView::mousemove_event() at the moment.

Libraries/LibHTML/Layout/LayoutNode.cpp

@@ -1,9 +1,11 @@
 #include <LibGUI/GPainter.h>
+#include <LibHTML/DOM/Document.h>
 #include <LibHTML/DOM/Element.h>
 #include <LibHTML/Layout/LayoutBlock.h>
 #include <LibHTML/Layout/LayoutNode.h>
 
 //#define DRAW_BOXES_AROUND_LAYOUT_NODES
+//#define DRAW_BOXES_AROUND_HOVERED_NODES
 
 LayoutNode::LayoutNode(const Node* node, StyleProperties&& style_properties)
     : m_node(node)
@@ -35,6 +37,10 @@ void LayoutNode::render(RenderingContext& context)
 {
 #ifdef DRAW_BOXES_AROUND_LAYOUT_NODES
     context.painter().draw_rect(m_rect, Color::Blue);
+#endif
+#ifdef DRAW_BOXES_AROUND_HOVERED_NODES
+    if (!is_anonymous() && node() == document().hovered_node())
+        context.painter().draw_rect(m_rect, Color::Red);
 #endif
     // TODO: render our background and border
     for_each_child([&](auto& child) {