**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

let serverValue;
      const propertyInfo = getPropertyInfo(propKey);
      if (suppressHydrationWarning) {
        
      } else if (
        propKey === SUPPRESS_CONTENT_EDITABLE_WARNING ||
        propKey === SUPPRESS_HYDRATION_WARNING ||
        
        
        propKey === 'value' ||
        propKey === 'checked' ||
        propKey === 'selected'
      ) {
        
      } else if (propKey === DANGEROUSLY_SET_INNER_HTML) {
        const serverHTML = domElement.innerHTML;
        const nextHtml = nextProp ? nextProp[HTML] : undefined;
        const expectedHTML = normalizeHTML(
          domElement,
          nextHtml != null ? nextHtml : '',
        );
        if (expectedHTML !== serverHTML) {
          warnForPropDifference(propKey, serverHTML, expectedHTML);
        }
      } else if (propKey === STYLE) {
        
        extraAttributeNames.delete(propKey);
        const expectedStyle = CSSPropertyOperations.createDangerousStringForStyles(
          nextProp,