LibWeb: Add Document.hasFocus() stub

This always returns true for now. A proper implementation needs to check
if the document is in the focused widget within an active window.

Userland/Libraries/LibWeb/DOM/Document.cpp

@@ -1147,4 +1147,10 @@ NonnullRefPtr<DOMImplementation> Document::implementation() const
     return *m_implementation;
 }
 
+bool Document::has_focus() const
+{
+    // FIXME: Return whether we actually have focus.
+    return true;
+}
+
 }

Userland/Libraries/LibWeb/DOM/Document.h

@@ -304,6 +304,8 @@ public:
     void evaluate_media_queries_and_report_changes();
     void add_media_query_list(NonnullRefPtr<CSS::MediaQueryList>&);
 
+    bool has_focus() const;
+
 private:
     explicit Document(const AK::URL&);
 

Userland/Libraries/LibWeb/DOM/Document.idl

@@ -2,6 +2,8 @@ interface Document : Node {
 
     constructor();
 
+    boolean hasFocus();
+
     // FIXME: These attributes currently don't do anything.
     [PutForwards=href, LegacyUnforgeable] readonly attribute Location? location;