LibWeb: Implement quirks mode detection

This allows us to determine which mode to render the page in.

Exposes "doctype" and "compatMode" on Document.
Exposes "name", "publicId" and "systemId" on DocumentType.

Libraries/LibWeb/DOM/Document.cpp

@@ -477,4 +477,20 @@ void Document::adopt_node(Node& subtree_root)
     });
 }
 
+const DocumentType* Document::doctype() const
+{
+    return first_child_of_type<DocumentType>();
+}
+
+const String& Document::compat_mode() const
+{
+    static String back_compat = "BackCompat";
+    static String css1_compat = "CSS1Compat";
+
+    if (m_quirks_mode == QuirksMode::Yes)
+        return back_compat;
+
+    return css1_compat;
+}
+
 }

Libraries/LibWeb/DOM/Document.h

@@ -43,6 +43,12 @@
 
 namespace Web {
 
+enum class QuirksMode {
+    No,
+    Limited,
+    Yes
+};
+
 class Document
     : public ParentNode
     , public NonElementParentNode<Document> {
@@ -142,11 +148,15 @@ public:
     void add_script_to_execute_as_soon_as_possible(Badge<HTMLScriptElement>, HTMLScriptElement&);
     NonnullRefPtrVector<HTMLScriptElement> take_scripts_to_execute_as_soon_as_possible(Badge<HTMLDocumentParser>);
 
-    bool in_quirks_mode() const { return m_quirks_mode; }
-    void set_quirks_mode(bool mode) { m_quirks_mode = mode; }
+    QuirksMode mode() const { return m_quirks_mode; }
+    bool in_quirks_mode() const { return m_quirks_mode == QuirksMode::Yes; }
+    void set_quirks_mode(QuirksMode mode) { m_quirks_mode = mode; }
 
     void adopt_node(Node&);
 
+    const DocumentType* doctype() const;
+    const String& compat_mode() const;
+
 private:
     virtual RefPtr<LayoutNode> create_layout_node(const StyleProperties* parent_style) override;
 
@@ -175,7 +185,7 @@ private:
     NonnullRefPtrVector<HTMLScriptElement> m_scripts_to_execute_when_parsing_has_finished;
     NonnullRefPtrVector<HTMLScriptElement> m_scripts_to_execute_as_soon_as_possible;
 
-    bool m_quirks_mode { false };
+    QuirksMode m_quirks_mode { QuirksMode::No };
 };
 
 template<>

Libraries/LibWeb/DOM/Document.idl

@@ -6,6 +6,9 @@ interface Document : Node {
     ArrayFromVector querySelectorAll(DOMString selectors);
     Element createElement(DOMString tagName);
 
+    readonly attribute DOMString compatMode;
+    readonly attribute DocumentType? doctype;
+
     readonly attribute HTMLElement? body;
 
 }

Libraries/LibWeb/DOM/DocumentType.h

@@ -33,6 +33,8 @@ namespace Web {
 
 class DocumentType final : public Node {
 public:
+    using WrapperType = Bindings::DocumentTypeWrapper;
+
     explicit DocumentType(Document&);
     virtual ~DocumentType() override;
 
@@ -41,8 +43,16 @@ public:
     const String& name() const { return m_name; }
     void set_name(const String& name) { m_name = name; }
 
+    const String& public_id() const { return m_public_id; }
+    void set_public_id(const String& public_id) { m_public_id = public_id; }
+
+    const String& system_id() const { return m_system_id; }
+    void set_system_id(const String& system_id) { m_system_id = system_id; }
+
 private:
     String m_name;
+    String m_public_id;
+    String m_system_id;
 };
 
 template<>

Libraries/LibWeb/DOM/DocumentType.idl

@@ -0,0 +1,7 @@
+interface DocumentType : Node {
+
+    readonly attribute DOMString name;
+    readonly attribute DOMString publicId;
+    readonly attribute DOMString systemId;
+
+}