**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
break;
    }
    assertValidProps(tag, rawProps, getCurrentFiberOwnerName);
    if (__DEV__) {
      var extraAttributeNames: Set<string> = new Set();
      var attributes = domElement.attributes;
      for (var i = 0; i < attributes.length; i++) {
        var name = attributes[i].name.toLowerCase();
        switch (name) {
          
          case 'data-reactroot':
            break;
          
          
          case 'value':
            break;
          case 'checked':
            break;
          case 'selected':
            break;
          default:
            
            
            extraAttributeNames.add(attributes[i].name);
        }
      }
    }
    var updatePayload = null;
    for (var propKey in rawProps) {
      if (!rawProps.hasOwnProperty(propKey)) {