**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

warnedUnknownTags[type] = true;
        warning(
          false,
          'The tag <%s> is unrecognized in this browser. ' +
            'If you meant to render a React component, start its name with ' +
            'an uppercase letter.',
          type,
        );
      }
    }
  }
  return domElement;
}
export function createTextNode(
  text: string,
  rootContainerElement: Element | Document,
): Text {
  return getOwnerDocumentFromRootContainer(rootContainerElement).createTextNode(
    text,
  );
}
export function setInitialProperties(
  domElement: Element,
  tag: string,
  rawProps: Object,
  rootContainerElement: Element | Document,
): void {
  const isCustomComponentTag = isCustomComponent(tag, rawProps);
  if (__DEV__) {
    validatePropertiesInDevelopment(tag, rawProps);