<!--
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
content::WebContents* web_contents,
                         Type type)
    : content::WebContentsObserver(web_contents),
      embedder_(nullptr),
      zoom_controller_(nullptr),
      type_(type),
      request_id_(0),
      background_throttling_(true),
      enable_devtools_(true) {
  if (type == REMOTE) {
    web_contents->SetUserAgentOverride(GetBrowserContext()->GetUserAgent());
    Init(isolate);
    AttachAsUserData(web_contents);
  } else {
    const mate::Dictionary options = mate::Dictionary::CreateEmpty(isolate);
    auto session = Session::CreateFrom(isolate, GetBrowserContext());
    session_.Reset(isolate, session.ToV8());
    InitWithSessionAndOptions(isolate, web_contents, session, options);
  }
}
WebContents::WebContents(v8::Isolate* isolate, const mate::Dictionary& options)