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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.cc
#include "atom/browser/common_web_contents_delegate.h"
#include <set>
#include <string>
#include <vector>
#include "atom/browser/atom_browser_context.h"
#include "atom/browser/atom_javascript_dialog_manager.h"
#include "atom/browser/native_window.h"
#include "atom/browser/ui/file_dialog.h"
#include "atom/browser/web_dialog_helper.h"
#include "atom/common/atom_constants.h"
#include "base/files/file_util.h"
#include "chrome/browser/printing/print_preview_message_handler.h"
#include "chrome/browser/printing/print_view_manager_basic.h"
#include "chrome/browser/ssl/security_state_tab_helper.h"
#include "chrome/browser/ui/browser_dialogs.h"
#include "chrome/common/pref_names.h"
#include "components/prefs/pref_service.h"