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* Electron version: 1.6.1
* Operating system: macOS

### Expected behavior

navigator.geolocation.getCurrentPosition runs in background

### Actual behavior

the entire UI is frozen

### How to reproduce

```js
    navigator.geolocation.getCurrentPosition((pos) => {
      console.log('POS: ' + pos);
    }, (err) => {
      console.log('Geolocation error: ', err);
    }, {enableHighAccuracy: false});
```
atom/browser/api/atom_api_web_contents.cc
Emit("will-destroy");
  
  RemoveFromWeakMap();
  
  
  MarkDestroyed();
  Emit("destroyed");
  
  base::ThreadTaskRunnerHandle::Get()->PostTask(
      FROM_HERE, GetDestroyClosure());
}
void WebContents::NavigationEntryCommitted(
    const content::LoadCommittedDetails& details) {
  Emit("navigation-entry-commited", details.entry->GetURL(),
       details.is_in_page, details.did_replace_entry);
}
int64_t WebContents::GetID() const {
  int64_t process_id = web_contents()->GetRenderProcessHost()->GetID();
  int64_t routing_id = web_contents()->GetRoutingID();
  int64_t rv = (process_id << 32) + routing_id;
  return rv;
}
int WebContents::GetProcessID() const {