**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

if (!nextProps.hasOwnProperty(propKey)) {
      continue;
    }
    const nextProp = nextProps[propKey];
    if (propKey === STYLE) {
      if (__DEV__) {
        if (nextProp) {
          
          
          Object.freeze(nextProp);
        }
      }
      
      CSSPropertyOperations.setValueForStyles(domElement, nextProp);
    } else if (propKey === DANGEROUSLY_SET_INNER_HTML) {
      const nextHtml = nextProp ? nextProp[HTML] : undefined;
      if (nextHtml != null) {
        setInnerHTML(domElement, nextHtml);
      }
    } else if (propKey === CHILDREN) {
      if (typeof nextProp === 'string') {
        
        
        
        
        const canSetTextContent = tag !== 'textarea' || nextProp !== '';
        if (canSetTextContent) {
          setTextContent(domElement, nextProp);
        }
      } else if (typeof nextProp === 'number') {