Fixing the instantiation of customized builtin elements (related to custom elements) (#9313)

* Fixing the creation of customized builtin elements

* Whitespace

* Running prettier

* Updating ReactDOMFiberComponent

src/renderers/dom/fiber/ReactDOMFiberComponent.js

@@ -439,7 +439,7 @@ var ReactDOMFiberComponent = {
         var firstChild = ((div.firstChild: any): HTMLScriptElement);
         domElement = div.removeChild(firstChild);
       } else if (props.is) {
-        domElement = ownerDocument.createElement(type, props.is);
+        domElement = ownerDocument.createElement(type, {is: props.is});
       } else {
         // Separate else branch instead of using `props.is || undefined` above because of a Firefox bug.
         // See discussion in https://github.com/facebook/react/pull/6896

src/renderers/dom/shared/__tests__/ReactDOMComponent-test.js

@@ -1071,10 +1071,9 @@ describe('ReactDOMComponent', () => {
         var container = document.createElement('div');
         spyOn(document, 'createElement').and.callThrough();
         ReactDOM.render(<div is="custom-div" />, container);
-        expect(document.createElement).toHaveBeenCalledWith(
-          'div',
-          'custom-div',
-        );
+        expect(document.createElement).toHaveBeenCalledWith('div', {
+          is: 'custom-div',
+        });
       } else {
         expect(
           ReactDOMServer.renderToString(<div is="custom-div" />),

src/renderers/dom/stack/client/ReactDOMComponent.js

@@ -552,7 +552,7 @@ ReactDOMComponent.Mixin = {
           div.innerHTML = `<${type}></${type}>`;
           el = div.removeChild(div.firstChild);
         } else if (props.is) {
-          el = ownerDocument.createElement(type, props.is);
+          el = ownerDocument.createElement(type, {is: props.is});
         } else {
           // Separate else branch instead of using `props.is || undefined` above because of a Firefox bug.
           // See discussion in https://github.com/facebook/react/pull/6896