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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
void OnEnterFullscreenModeForTab(content::WebContents* source,
                                   const GURL& origin,
                                   bool allowed);
  
  void OnCreateWindow(
      const GURL& target_url,
      const std::string& frame_name,
      WindowOpenDisposition disposition,
      const std::vector<std::string>& features,
      const scoped_refptr<content::ResourceRequestBodyImpl>& body);
  
  v8::Local<v8::Value> GetWebPreferences(v8::Isolate* isolate);
  
  v8::Local<v8::Value> GetOwnerBrowserWindow();
  
  int32_t ID() const;
  v8::Local<v8::Value> Session(v8::Isolate* isolate);
  content::WebContents* HostWebContents();
  v8::Local<v8::Value> DevToolsWebContents(v8::Isolate* isolate);
  v8::Local<v8::Value> Debugger(v8::Isolate* isolate);
  WebContentsZoomController* GetZoomController() { return zoom_controller_; }
 protected:
  WebContents(v8::Isolate* isolate,
              content::WebContents* web_contents,
              Type type);
  WebContents(v8::Isolate* isolate, const mate::Dictionary& options);
  ~WebContents();
  void InitWithSessionAndOptions(v8::Isolate* isolate,
                                 content::WebContents *web_contents,
                                 mate::Handle<class Session> session,