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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
content::WebContents *web_contents,
                                            mate::Handle<api::Session> session,
                                            const mate::Dictionary& options) {
  content::WebContentsObserver::Observe(web_contents);
  InitWithWebContents(web_contents, session->browser_context());
  managed_web_contents()->GetView()->SetDelegate(this);
  
  new WebContentsPreferences(web_contents, options);
  
  WebContentsPermissionHelper::CreateForWebContents(web_contents);
  
  SecurityStateTabHelper::CreateForWebContents(web_contents);
  
  WebContentsZoomController::CreateForWebContents(web_contents);
  zoom_controller_ = WebContentsZoomController::FromWebContents(web_contents);
  double zoom_factor;
  if (options.Get(options::kZoomFactor, &zoom_factor))
    zoom_controller_->SetDefaultZoomFactor(zoom_factor);
  web_contents->SetUserAgentOverride(GetBrowserContext()->GetUserAgent());
  if (IsGuest()) {
    guest_delegate_->Initialize(this);
    NativeWindow* owner_window = nullptr;
    if (options.Get("embedder", &embedder_) && embedder_) {