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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.cc
const content::SavePageType& save_type,
                           const SavePageHandler::SavePageCallback& callback) {
  auto handler = new SavePageHandler(web_contents(), callback);
  return handler->Handle(full_file_path, save_type);
}
void WebContents::OpenDevTools(mate::Arguments* args) {
  if (type_ == REMOTE)
    return;
  if (!enable_devtools_)
    return;
  std::string state;
  if (type_ == WEB_VIEW || !owner_window()) {
    state = "detach";
  } else if (args && args->Length() == 1) {
    bool detach = false;
    mate::Dictionary options;
    if (args->GetNext(&options)) {
      options.Get("mode", &state);
      
      options.Get("detach", &detach);
      if (state.empty() && detach)
        state = "detach";
    }
  }
  managed_web_contents()->SetDockState(state);
  managed_web_contents()->ShowDevTools();
}
void WebContents::CloseDevTools() {