**Do you want to request a *feature* or report a *bug*?**
*Feature*

**What is the current behavior?**
In Firefox the `dialog` element is not implemented. We use a polyfill to be able to support it. Everything works well. But React warns that the `dialog` element is unrecognized, and this on each page load, which is quite useless (for this specific case).
I would like the possibility to disable the  warning but only for some elements. So the utility of this warning remains when the developer mistype the component name.

**What is the expected behavior?**
Once we specified which tag are "accepted/normal" React will not warn on specified unrecognized tags.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
React 16
Firefox 57

In previous versions there was no warning.

Is this clear enough? Do you need any other information?
Cheers
}
var ReactDOMFiberComponent = {
  createElement(
    type: *,
    props: Object,
    rootContainerElement: Element | Document,
    parentNamespace: string,
  ): Element {
    
    
    var ownerDocument: Document = getOwnerDocumentFromRootContainer(
      rootContainerElement,
    );
    var domElement: Element;
    var namespaceURI = parentNamespace;
    if (namespaceURI === HTML_NAMESPACE) {
      namespaceURI = getIntrinsicNamespace(type);
    }
    if (namespaceURI === HTML_NAMESPACE) {
      if (__DEV__) {
        var isCustomComponentTag = isCustomComponent(type, props);
        
        
        warning(
          isCustomComponentTag || type === type.toLowerCase(),
          '<%s /> is using uppercase HTML. Always use lowercase HTML tags ' +
            'in React.',
          type,
        );
      }