**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

nextProps.hasOwnProperty(propKey) ||
      !lastProps.hasOwnProperty(propKey) ||
      lastProps[propKey] == null
    ) {
      continue;
    }
    if (propKey === STYLE) {
      const lastStyle = lastProps[propKey];
      for (styleName in lastStyle) {
        if (lastStyle.hasOwnProperty(styleName)) {
          if (!styleUpdates) {
            styleUpdates = {};
          }
          styleUpdates[styleName] = '';
        }
      }
    } else if (propKey === DANGEROUSLY_SET_INNER_HTML || propKey === CHILDREN) {
      
    } else if (
      propKey === SUPPRESS_CONTENT_EDITABLE_WARNING ||
      propKey === SUPPRESS_HYDRATION_WARNING
    ) {
      
    } else if (propKey === AUTOFOCUS) {
      
    } else if (registrationNameModules.hasOwnProperty(propKey)) {
      
      
      
      if (!updatePayload) {