**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
false,
            'The tag <%s> is unrecognized in this browser. ' +
              'If you meant to render a React component, start its name with ' +
              'an uppercase letter.',
            type,
          );
        }
      }
    }
    return domElement;
  },
  createTextNode(text: string, rootContainerElement: Element | Document): Text {
    return getOwnerDocumentFromRootContainer(
      rootContainerElement,
    ).createTextNode(text);
  },
  setInitialProperties(
    domElement: Element,
    tag: string,
    rawProps: Object,
    rootContainerElement: Element | Document,
  ): void {
    var isCustomComponentTag = isCustomComponent(tag, rawProps);
    if (__DEV__) {
      validatePropertiesInDevelopment(tag, rawProps);
      if (isCustomComponentTag && !didWarnShadyDOM && domElement.shadyRoot) {
        warning(
          false,
          '%s is using shady DOM. Using shady DOM with React can ' +
            'cause things to break subtly.',