LibWeb: Add fast_is<T>() for some common DOM Node subclasses

Userland/Libraries/LibWeb/DOM/Comment.h

@@ -23,4 +23,7 @@ public:
     static NonnullRefPtr<Comment> create_with_global_object(Bindings::WindowObject& window, String const& data);
 };
 
+template<>
+inline bool Node::fast_is<Comment>() const { return is_comment(); }
+
 }

Userland/Libraries/LibWeb/DOM/DocumentFragment.h

@@ -36,4 +36,7 @@ private:
     WeakPtr<Element> m_host;
 };
 
+template<>
+inline bool Node::fast_is<DocumentFragment>() const { return is_document_fragment(); }
+
 }

Userland/Libraries/LibWeb/DOM/DocumentType.h

@@ -43,4 +43,7 @@ private:
     String m_system_id;
 };
 
+template<>
+inline bool Node::fast_is<DocumentType>() const { return is_document_type(); }
+
 }

Userland/Libraries/LibWeb/DOM/ProcessingInstruction.h

@@ -26,4 +26,7 @@ private:
     String m_target;
 };
 
+template<>
+inline bool Node::fast_is<ProcessingInstruction>() const { return node_type() == (u16)NodeType::PROCESSING_INSTRUCTION_NODE; }
+
 }

Userland/Libraries/LibWeb/DOM/Text.h

@@ -38,4 +38,7 @@ private:
     bool m_always_editable { false };
 };
 
+template<>
+inline bool Node::fast_is<Text>() const { return is_text(); }
+
 }