* Electron version: 2.0.0-beta.4
* Operating system: macOS 10.13.3

### Expected behavior

A reload of the window works.

### Actual behavior

A reload of the window does not work.

### How to reproduce

* run VSCode exploration ([download](https://az764295.vo.msecnd.net/exploration/6bc3274250cc949c7fb1d654cbb6e59c8ddad697/VSCode-darwin-exploration.zip))
* run "Reload Window" command
* sometimes I see the window stay blank after doing so and checking the console I see:

```
Uncaught (in promise) Error: Cannot get property 'id' on missing remote object 3
Error: Cannot get property 'id' on missing remote object 3
    at throwRPCError (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/rpc-server.js:143:17)
    at EventEmitter.<anonymous> (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/rpc-server.js:384:7)
    at emitThree (events.js:136:13)
    at EventEmitter.emit (events.js:217:7)
    at WebContents.<anonymous> (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/api/web-contents.js:295:13)
    at emitTwo (events.js:126:13)
    at WebContents.emit (events.js:214:7)
    at throwRPCError (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/rpc-server.js:143:17)
    at EventEmitter.<anonymous> (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/rpc-server.js:384:7)
    at emitThree (events.js:136:13)
    at EventEmitter.emit (events.js:217:7)
    at WebContents.<anonymous> (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/api/web-contents.js:295:13)
    at emitTwo (events.js:126:13)
    at WebContents.emit (events.js:214:7)
    at Object.exception (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/renderer/api/remote.js:209:30)
    at metaToValue (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/renderer/api/remote.js:213:28)
    at Object.descriptor.get [as id] (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/renderer/api/remote.js:132:16)
    at file:///Applications/Visual%20Studio%20Code%20-%20Exploration.app/Contents/Resources/app/out/vs/workbench/electron-browser/bootstrap/index.js:11:97
    at new Promise (<anonymous>)
    at file:///Applications/Visual%20Studio%20Code%20-%20Exploration.app/Contents/Resources/app/out/vs/workbench/electron-browser/bootstrap/index.js:10:838
```
atom/browser/atom_browser_client.cc
}
  }
  
  auto src_url = current_instance->GetSiteURL();
  return
      !content::SiteInstance::IsSameWebSite(browser_context, src_url, url) &&
      
      
      
      content::SiteInstance::GetSiteForURL(browser_context, url) != src_url;
}
void AtomBrowserClient::AddProcessPreferences(
    int process_id, AtomBrowserClient::ProcessPreferences prefs) {
  process_preferences_[process_id] = prefs;
}
void AtomBrowserClient::RemoveProcessPreferences(int process_id) {
  process_preferences_.erase(process_id);
}
bool AtomBrowserClient::IsProcessObserved(int process_id) {
  return process_preferences_.find(process_id) != process_preferences_.end();
}
bool AtomBrowserClient::IsRendererSandboxed(int process_id) {
  auto it = process_preferences_.find(process_id);
  return it != process_preferences_.end() && it->second.sandbox;
}
bool AtomBrowserClient::RendererUsesNativeWindowOpen(int process_id) {
  auto it = process_preferences_.find(process_id);
  return it != process_preferences_.end() && it->second.native_window_open;
}
bool AtomBrowserClient::RendererDisablesPopups(int process_id) {