**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
if (didWarnInvalidHydration) {
      return;
    }
    didWarnInvalidHydration = true;
    warning(
      false,
      'Text content did not match. Server: "%s" Client: "%s"',
      serverText,
      clientText,
    );
  };
  var warnForPropDifference = function(
    propName: string,
    serverValue: mixed,
    clientValue: mixed,
  ) {
    if (didWarnInvalidHydration) {
      return;
    }
    didWarnInvalidHydration = true;
    warning(
      false,
      'Prop `%s` did not match. Server: %s Client: %s',
      propName,
      JSON.stringify(serverValue),
      JSON.stringify(clientValue),
    );
  };
  var warnForExtraAttributes = function(attributeNames: Set<string>) {
    if (didWarnInvalidHydration) {