Is it legal to register a type extension on top of an existing custom tag? <x-button is="x-submit-button"></x-button>
var ButtonPrototype = Object.create(HTMLElement.prototype) document.registerElement("x-button", {prototype: ButtonPrototype}) var SubmitButtonPrototype = Object.create(ButtonPrototype) document.registerElement("x-submit-button", {extends: "x-button", prototype: SubmitButtonPrototype}) Chrome's native registerElement doesn't seem to like this. It throws the following error. DOMException: Failed to execute 'registerElement' on 'Document': Registration failed for type 'x-submit-button'. The tag name specified in 'extends' is a custom element name. Use inheritance instead. The current Custom Element spec doesn't say any specific about this situation. Is Chrome wrong? Or is this something the spec should explicitly disallow?