LibWeb: Move setting of Web object prototypes to initialize()

This needs to happen before prototype/constructor intitialization can be
made lazy. Otherwise, GC could run during the C++ constructor and try to
collect the object currently being created.

Userland/Libraries/LibWeb/HTML/HTMLButtonElement.h

@@ -26,6 +26,8 @@ class HTMLButtonElement final
 public:
     virtual ~HTMLButtonElement() override;
 
+    virtual void initialize(JS::Realm&) override;
+
     enum class TypeAttributeState {
 #define __ENUMERATE_HTML_BUTTON_TYPE_ATTRIBUTE(_, state) state,
         ENUMERATE_HTML_BUTTON_TYPE_ATTRIBUTES