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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.h
content::NavigationController::LoadURLParams params;
    int id;
  };
  AtomBrowserContext* GetBrowserContext() const;
  uint32_t GetNextRequestId() {
    return ++request_id_;
  }
  
  void OnCursorChange(const content::WebCursor& cursor);
  
  void OnRendererMessage(const base::string16& channel,
                         const base::ListValue& args);
  
  void OnRendererMessageSync(const base::string16& channel,
                             const base::ListValue& args,
                             IPC::Message* message);