**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

case 'data-reactroot':
          break;
        
        
        case 'value':
          break;
        case 'checked':
          break;
        case 'selected':
          break;
        default:
          // Intentionally use the original name.
          // See discussion in https://github.com/facebook/react/pull/10676.
          extraAttributeNames.add(attributes[i].name);
      }
    }
  }
  let updatePayload = null;
  for (const propKey in rawProps) {
    if (!rawProps.hasOwnProperty(propKey)) {
      continue;
    }
    const nextProp = rawProps[propKey];
    if (propKey === CHILDREN) {
      // For text content children we compare against textContent. This
      // might match additional HTML that is hidden when we read it using
      // textContent. E.g. "foo" will match "f<span>oo</span>" but that still
      // satisfies our requirement. Our requirement is not to produce perfect
      // HTML and attributes. Ideally we should preserve structure but it's