**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 (
      isCustomComponentTag &&
      !didWarnShadyDOM &&
      (domElement: any).shadyRoot
    ) {
      warning(
        false,
        '%s is using shady DOM. Using shady DOM with React can ' +
          'cause things to break subtly.',
        getCurrentFiberOwnerNameInDevOrNull() || 'A component',
      );
      didWarnShadyDOM = true;
    }
  }
  
  let props: Object;
  switch (tag) {
    case 'iframe':
    case 'object':
      trapBubbledEvent(TOP_LOAD, domElement);
      props = rawProps;
      break;
    case 'video':
    case 'audio':
      
      for (let i = 0; i < mediaEventTypes.length; i++) {
        trapBubbledEvent(mediaEventTypes[i], domElement);
      }
      props = rawProps;