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

**What is the current behavior?**

Since React@16.5 seems that `root` element has `onclick` event handler with noop function.
In ios Safari/Chrome browsers html element has gray overlay when tap on it.

The current behavior is that the whole `root` is blinking when we tap on it.

The simple example to reproduce:
https://codesandbox.io/s/wyo8rlj1zk
The issue is reproducing only in fullscreen mode https://wyo8rlj1zk.codesandbox.io/
(root container is steel blue)

I suppose changes came from here:
https://github.com/facebook/react/pull/11927
https://github.com/facebook/react/pull/11927/files

and the issue can be related with:
https://github.com/mui-org/material-ui/issues/11154
https://github.com/facebook/react/issues/12717

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
React 16.5
ios 11.3/12 Safari/Chrome
container._reactRootContainer = null;
        });
      });
      
      
      return true;
    } else {
      if (__DEV__) {
        const rootEl = getReactRootElementInContainer(container);
        const hasNonRootReactChild = !!(
          rootEl && ReactDOMComponentTree.getInstanceFromNode(rootEl)
        );
        
        const isContainerReactRoot =
          container.nodeType === ELEMENT_NODE &&
          isValidContainer(container.parentNode) &&
          !!container.parentNode._reactRootContainer;
        warningWithoutStack(
          !hasNonRootReactChild,
          "unmountComponentAtNode(): The node you're attempting to unmount " +
            'was rendered by React and is not a top-level container. %s',
          isContainerReactRoot
            ? 'You may have accidentally passed in a React root node instead ' +
              'of its container.'
            : 'Instead, have the parent component update its state and ' +
              'rerender in order to remove this component.',
        );
      }
      return false;
    }