LibWeb+WebContent: Hook document.cookie to the backend cookie storage

Author: https://github.com/trflynn89
Commit: 1ef48d50ff
Pull-request: https://github.com/SerenityOS/serenity/pull/6240

Userland/Libraries/LibWeb/DOM/Document.h

@@ -73,7 +73,7 @@ public:
 
     virtual ~Document() override;
 
-    String cookie() const;
+    String cookie();
     void set_cookie(String);
 
     bool should_invalidate_styles_on_attribute_changes() const { return m_should_invalidate_styles_on_attribute_changes; }