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

**What is the current behavior?**
In mobile Safari, DOM events originating from elements rendered through a Portal do **not** bubble (propagate) up the React component tree.

**If the current behavior is a bug, please provide the steps to reproduce....**
Please see the following JSFiddle: https://jsfiddle.net/zebulonj/wf7orwan/

In this JSFiddle, the expected behavior (seen in a desktop browser) is that clicking on the portal content (appearing as a modal, including backdrop) should toggle to the "On" or "Off" indicator rendered in the main content. However, in mobile Safari (iOS 11.1.1), the click events do not propagate.


**What is the expected behavior?**
Click events should propagate up the React component tree.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
Affected: React 16.2
iOS 11.1.1

createElement,
  createTextNode,
  setInitialProperties,
  diffProperties,
  updateProperties,
  diffHydratedProperties,
  diffHydratedText,
  warnForUnmatchedText,
  warnForDeletedHydratableElement,
  warnForDeletedHydratableText,
  warnForInsertedHydratedElement,
  warnForInsertedHydratedText,
} from './ReactDOMFiberComponent';
import * as ReactInputSelection from './ReactInputSelection';
import setTextContent from './setTextContent';
import {validateDOMNesting, updatedAncestorInfo} from './validateDOMNesting';
import * as ReactBrowserEventEmitter from '../events/ReactBrowserEventEmitter';
import {getChildNamespace} from '../shared/DOMNamespaces';
import {
  ELEMENT_NODE,
  TEXT_NODE,
  COMMENT_NODE,
  DOCUMENT_NODE,
  DOCUMENT_FRAGMENT_NODE,
} from '../shared/HTMLNodeType';
export type Type = string;
export type Props = {
  autoFocus?: boolean,
  children?: mixed,
  hidden?: boolean,