<!--
Thanks for opening an issue! A few things to keep in mind:

- The issue tracker is only for bugs and feature requests.
- Before reporting a bug, please try reproducing your issue against
  the latest version of Electron.
- If you need general advice, join our Slack: http://atom-slack.herokuapp.com
-->

* 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
bool explicit_set) {
  if (entry)
    Emit("-page-title-updated", entry->GetTitle(), explicit_set);
  else
    Emit("-page-title-updated", "", explicit_set);
}
void WebContents::DidUpdateFaviconURL(
    const std::vector<content::FaviconURL>& urls) {
  std::set<GURL> unique_urls;
  for (const auto& iter : urls) {
    if (iter.icon_type != content::FaviconURL::FAVICON)
      continue;
    const GURL& url = iter.icon_url;
    if (url.is_valid())
      unique_urls.insert(url);
  }
  Emit("page-favicon-updated", unique_urls);
}
void WebContents::Observe(int type,