**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
return;
    }
    didWarnInvalidHydration = true;
    var names = [];
    attributeNames.forEach(function(name) {
      names.push(name);
    });
    warning(false, 'Extra attributes from the server: %s', names);
  };
  var warnForInvalidEventListener = function(registrationName, listener) {
    warning(
      false,
      'Expected `%s` listener to be a function, instead got a value of `%s` type.%s',
      registrationName,
      typeof listener,
      getCurrentFiberStackAddendum(),
    );
  };
  var testDocument;
  
  
  var normalizeHTML = function(parent: Element, html: string) {
    if (!testDocument) {
      
      testDocument = document.implementation.createHTMLDocument('');