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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 Print(mate::Arguments* args);
  void SetEmbedder(const WebContents* embedder);
  
  void PrintToPDF(const base::DictionaryValue& setting,
                  const PrintToPDFCallback& callback);
  
  void AddWorkSpace(mate::Arguments* args, const base::FilePath& path);
  void RemoveWorkSpace(mate::Arguments* args, const base::FilePath& path);
  
  void Undo();
  void Redo();
  void Cut();
  void Copy();
  void Paste();
  void PasteAndMatchStyle();
  void Delete();
  void SelectAll();
  void Unselect();
  void Replace(const base::string16& word);
  void ReplaceMisspelling(const base::string16& word);
  uint32_t FindInPage(mate::Arguments* args);
  void StopFindInPage(content::StopFindAction action);
  void ShowDefinitionForSelection();
  void CopyImageAt(int x, int y);
  
  void Focus();
  bool IsFocused() const;
  void TabTraverse(bool reverse);
  
  bool SendIPCMessage(bool all_frames,