* Electron version: 1.6.3
* Operating system: Linux

### Expected behavior

When registering a `beforeunload` handler which cancels unloading, I would expect the handler to be called for every `BrowserWindow.reload()`.

### Actual behavior

On 1.6.3, the `beforeunload` handler is called for the first `reload` but not on subsequent calls. Even after removing the event handler, `reload` will not reload the window anymore.

### How to reproduce

```javascript
const cancelUnload = e => {
   console.log('cancelUnload called')
   e.returnValue = false
}

window.addEventListener('beforeunload', cancelUnload)

remote.getCurrentWindow().reload()  // [1] -> cancelUnload called
remote.getCurrentWindow().reload()  // [2] -> cancelUnload called

remote.getCurrentWindow().close()   // [3] -> cancelUnload called
remote.getCurrentWindow().close()   // [4] -> cancelUnload called

window.removeEventListener('beforeunload', cancelUnload)

remote.getCurrentWindow().reload()  // [5] -> reloads window

remote.getCurrentWindow().close()   // [6] -> closes window
```
I would expect `cancelUnload` to be printed to the console four times and the step at `[5]` to actually reload the window. This is works up to Electron 1.6.2.

On Electron 1.6.3 `cancelUnload` is not printed at step `[2]` (nor on any subsequent calls to reload). What's more, event after removing the `beforeunload` handler, `reload` does not work anymore: at step `[5]` the window does not reload (but closing the window at `[6]` works).
atom/browser/api/atom_api_web_contents.cc
atom::AtomBrowserClient::SuppressRendererProcessRestartForOnce();
  web_contents()->GetController().GoToOffset(offset);
}
const std::string WebContents::GetWebRTCIPHandlingPolicy() const {
  return web_contents()->
    GetMutableRendererPrefs()->webrtc_ip_handling_policy;
}
void WebContents::SetWebRTCIPHandlingPolicy(
    const std::string& webrtc_ip_handling_policy) {
  if (GetWebRTCIPHandlingPolicy() == webrtc_ip_handling_policy)
    return;
  web_contents()->GetMutableRendererPrefs()->webrtc_ip_handling_policy =
    webrtc_ip_handling_policy;
  content::RenderViewHost* host = web_contents()->GetRenderViewHost();
  if (host)
    host->SyncRendererPrefs();
}
bool WebContents::IsCrashed() const {
  return web_contents()->IsCrashed();
}
void WebContents::SetUserAgent(const std::string& user_agent,
                               mate::Arguments* args) {
  web_contents()->SetUserAgentOverride(user_agent);
}
std::string WebContents::GetUserAgent() {
  return web_contents()->GetUserAgentOverride();
}
bool WebContents::SavePage(const base::FilePath& full_file_path,