**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

const ownerDocument: Document = getOwnerDocumentFromRootContainer(
    rootContainerElement,
  );
  let domElement: Element;
  let namespaceURI = parentNamespace;
  if (namespaceURI === HTML_NAMESPACE) {
    namespaceURI = getIntrinsicNamespace(type);
  }
  if (namespaceURI === HTML_NAMESPACE) {
    if (__DEV__) {
      isCustomComponentTag = isCustomComponent(type, props);
      
      
      warning(
        isCustomComponentTag || type === type.toLowerCase(),
        '<%s /> is using incorrect casing. ' +
          'Use PascalCase for React components, ' +
          'or lowercase for HTML elements.',
        type,
      );
    }
    if (type === 'script') {
      
      
      const div = ownerDocument.createElement('div');
      div.innerHTML = '<script><' + '/script>'; 
      
      const firstChild = ((div.firstChild: any): HTMLScriptElement);