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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/common_web_contents_delegate.h
return web_contents_.get();
  }
  NativeWindow* owner_window() const { return owner_window_.get(); }
  bool is_html_fullscreen() const { return html_fullscreen_; }
 protected:
  
  content::WebContents* OpenURLFromTab(
      content::WebContents* source,
      const content::OpenURLParams& params) override;
  bool CanOverscrollContent() const override;
  content::JavaScriptDialogManager* GetJavaScriptDialogManager(
      content::WebContents* source) override;
  content::ColorChooser* OpenColorChooser(
      content::WebContents* web_contents,
      SkColor color,