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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::NavigationHandle* navigation_handle) {
  if (!navigation_handle->IsInMainFrame() || navigation_handle->IsSamePage())
    return;
  if (deferred_load_url_.id) {
    auto web_contents = navigation_handle->GetWebContents();
    auto& controller = web_contents->GetController();
    int id = controller.GetPendingEntry()->GetUniqueID();
    if (id == deferred_load_url_.id) {
      if (!deferred_load_url_.params.url.is_empty()) {
        auto params = deferred_load_url_.params;
        deferred_load_url_.id = 0;
        deferred_load_url_.params =
            content::NavigationController::LoadURLParams(GURL());
        controller.LoadURLWithParams(params);
        SetBackgroundColor(web_contents);
      } else {
        deferred_load_url_.id = 0;
      }
    }
  }
}
void WebContents::DidFinishNavigation(