**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

for (styleName in nextProp) {
          if (
            nextProp.hasOwnProperty(styleName) &&
            lastProp[styleName] !== nextProp[styleName]
          ) {
            if (!styleUpdates) {
              styleUpdates = {};
            }
            styleUpdates[styleName] = nextProp[styleName];
          }
        }
      } else {
        
        if (!styleUpdates) {
          if (!updatePayload) {
            updatePayload = [];
          }
          updatePayload.push(propKey, styleUpdates);
        }
        styleUpdates = nextProp;
      }
    } else if (propKey === DANGEROUSLY_SET_INNER_HTML) {
      const nextHtml = nextProp ? nextProp[HTML] : undefined;
      const lastHtml = lastProp ? lastProp[HTML] : undefined;
      if (nextHtml != null) {
        if (lastHtml !== nextHtml) {
          (updatePayload = updatePayload || []).push(propKey, '' + nextHtml);
        }
      } else {