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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
}
namespace content {
class ResourceRequestBodyImpl;
}
namespace mate {
class Arguments;
class Dictionary;
}
namespace atom {
struct SetSizeParams;
class AtomBrowserContext;
class WebContentsZoomController;
class WebViewGuestDelegate;
namespace api {
class WebContents : public mate::TrackableObject<WebContents>,
                    public CommonWebContentsDelegate,
                    public content::WebContentsObserver,
                    public content::NotificationObserver {
 public:
  enum Type {