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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
session = Session::FromPartition(isolate, "");
  }
  session_.Reset(isolate, session.ToV8());
  content::WebContents* web_contents;
  if (IsGuest()) {
    scoped_refptr<content::SiteInstance> site_instance =
        content::SiteInstance::CreateForURL(
            session->browser_context(), GURL("chrome-guest://fake-host"));
    content::WebContents::CreateParams params(
        session->browser_context(), site_instance);
    guest_delegate_.reset(new WebViewGuestDelegate);
    params.guest_delegate = guest_delegate_.get();
    web_contents = content::WebContents::Create(params);
  } else if (IsOffScreen()) {
    bool transparent = false;
    options.Get("transparent", &transparent);
    content::WebContents::CreateParams params(session->browser_context());
    auto* view = new OffScreenWebContentsView(
        transparent, base::Bind(&WebContents::OnPaint, base::Unretained(this)));
    params.view = view;
    params.delegate_view = view;
    web_contents = content::WebContents::Create(params);
    view->SetWebContents(web_contents);
  } else {
    content::WebContents::CreateParams params(session->browser_context());
    web_contents = content::WebContents::Create(params);
  }
  InitWithSessionAndOptions(isolate, web_contents, session, options);
}
void WebContents::InitWithSessionAndOptions(v8::Isolate* isolate,