LibWeb: Add fast_is<T>() for some DOM and layout node subclasses

The generic is<T>() uses dynamic_cast which is fine in the majority
of cases, but when one of them shows up in profiles, we can make it
faster by answering the is-a question manually.

1 files changed, 4 insertions, 0 deletions

diff --git a/Userland/Libraries/LibWeb/Layout/TextNode.h b/Userland/Libraries/LibWeb/Layout/TextNode.h
index 03781a22b2..f7c6282957 100644
--- a/Userland/Libraries/LibWeb/Layout/TextNode.h
+++ b/Userland/Libraries/LibWeb/Layout/TextNode.h
@@ -47,6 +47,7 @@ public:
     virtual void split_into_lines(InlineFormattingContext&, LayoutMode) override;
 
 private:
+    virtual bool is_text_node() const final { return true; }
     void split_into_lines_by_rules(InlineFormattingContext&, LayoutMode, bool do_collapse, bool do_wrap_lines, bool do_wrap_breaks);
     void paint_cursor_if_needed(PaintContext&, const LineBoxFragment&) const;
 
@@ -56,4 +57,7 @@ private:
     String m_text_for_rendering;
 };
 
+template<>
+inline bool Node::fast_is<TextNode>() const { return is_text_node(); }
+
 }