**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

type = container.tagName;
      namespace = getChildNamespace(ownNamespace, type);
      break;
    }
  }
  if (__DEV__) {
    const validatedTag = type.toLowerCase();
    const ancestorInfo = updatedAncestorInfo(null, validatedTag);
    return {namespace, ancestorInfo};
  }
  return namespace;
}
export function getChildHostContext(
  parentHostContext: HostContext,
  type: string,
  rootContainerInstance: Container,
): HostContext {
  if (__DEV__) {
    const parentHostContextDev = ((parentHostContext: any): HostContextDev);
    const namespace = getChildNamespace(parentHostContextDev.namespace, type);
    const ancestorInfo = updatedAncestorInfo(
      parentHostContextDev.ancestorInfo,
      type,
    );
    return {namespace, ancestorInfo};
  }
  const parentNamespace = ((parentHostContext: any): HostContextProd);
  return getChildNamespace(parentNamespace, type);
}
export function getPublicInstance(instance: Instance): * {