<!--
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
Emit("devtools-reload-page");
}
void WebContents::DevToolsFocused() {
  Emit("devtools-focused");
}
void WebContents::DevToolsOpened() {
  v8::Locker locker(isolate());
  v8::HandleScope handle_scope(isolate());
  auto handle = WebContents::CreateFrom(
      isolate(), managed_web_contents()->GetDevToolsWebContents());
  devtools_web_contents_.Reset(isolate(), handle.ToV8());
  
  base::FundamentalValue tab_id(ID());
  managed_web_contents()->CallClientFunction(
      "DevToolsAPI.setInspectedTabId", &tab_id, nullptr, nullptr);
  
  if (owner_window())
    handle->SetOwnerWindow(managed_web_contents()->GetDevToolsWebContents(),
                           owner_window());
  Emit("devtools-opened");
}
void WebContents::DevToolsClosed() {