* Electron version: 1.6.15
* Operating system: Linux

### Expected behavior

Open a `BrowserWindow` with passed options

### Actual behavior

  - Usually a Segmentation fault.
  - Sometimes `[12843:0100/000000.043847:FATAL:zygote_linux.cc(479)] Failed to synchronise with parent zygote process`
  - Sometimes `[12819:0100/000000.719122:FATAL:zygote_linux.cc(509)] Check failed: len > 0 (0 vs. 0)`

### How to reproduce

I'm still working on making a smaller reproduction case. The issue goes away with small tweaks.

1. Starting from https://github.com/daurnimator/fengari-electron-example
2. Modify main.lua to contain:
```lua
local js = require "js"
local electron = require "electron"

electron.app:on("ready", function()
	local win = js.new(electron.BrowserWindow, js.createproxy({
		backgroundColor = '#2e2c29';
	}, "object"))
	win:loadURL("https://fengari.io")
end)
```

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,