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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
Emit("did-start-loading");
}
void WebContents::DidStopLoading() {
  Emit("did-stop-loading");
}
void WebContents::DidGetResourceResponseStart(
    const content::ResourceRequestDetails& details) {
  Emit("did-get-response-details",
       details.socket_address.IsEmpty(),
       details.url,
       details.original_url,
       details.http_response_code,
       details.method,
       details.referrer,
       details.headers.get(),
       ResourceTypeToString(details.resource_type));
}
void WebContents::DidGetRedirectForResourceRequest(
    const content::ResourceRedirectDetails& details) {
  Emit("did-get-redirect-request",
       details.url,
       details.new_url,
       (details.resource_type == content::RESOURCE_TYPE_MAIN_FRAME),
       details.http_response_code,
       details.method,
       details.referrer,
       details.headers.get());
}
void WebContents::DidStartNavigation(