<!--
Thanks for opening an issue! A few things to keep in mind:

- The issue tracker is only for bugs and feature requests.
- Before reporting a bug, please try reproducing your issue against
  the latest version of Electron.
- If you need general advice, join our Slack: http://atom-slack.herokuapp.com
-->

* 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
CommonWebContentsDelegate::ExitFullscreenModeForTab(source);
  Emit("leave-html-full-screen");
}
void WebContents::RendererUnresponsive(
    content::WebContents* source,
    const content::WebContentsUnresponsiveState& unresponsive_state) {
  Emit("unresponsive");
  if ((type_ == BROWSER_WINDOW || type_ == OFF_SCREEN) && owner_window())
    owner_window()->RendererUnresponsive(source);
}
void WebContents::RendererResponsive(content::WebContents* source) {
  Emit("responsive");
  if ((type_ == BROWSER_WINDOW || type_ == OFF_SCREEN) && owner_window())
    owner_window()->RendererResponsive(source);
}
bool WebContents::HandleContextMenu(const content::ContextMenuParams& params) {
  if (params.custom_context.is_pepper_menu) {
    Emit("pepper-context-menu", std::make_pair(params, web_contents()));
    web_contents()->NotifyContextMenuClosed(params.custom_context);
  } else {
    Emit("context-menu", std::make_pair(params, web_contents()));
  }
  return true;
}
bool WebContents::OnGoToEntryOffset(int offset) {