**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

export function hydrateInstance(
  instance: Instance,
  type: string,
  props: Props,
  rootContainerInstance: Container,
  hostContext: HostContext,
  internalInstanceHandle: Object,
): null | Array<mixed> {
  precacheFiberNode(internalInstanceHandle, instance);
  
  
  updateFiberProps(instance, props);
  let parentNamespace: string;
  if (__DEV__) {
    const hostContextDev = ((hostContext: any): HostContextDev);
    parentNamespace = hostContextDev.namespace;
  } else {
    parentNamespace = ((hostContext: any): HostContextProd);
  }
  return diffHydratedProperties(
    instance,
    type,
    props,
    parentNamespace,
    rootContainerInstance,
  );
}
export function hydrateTextInstance(
  textInstance: TextInstance,
  text: string,