* 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
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::Value tab_id(ID());
  managed_web_contents()->CallClientFunction(
      "DevToolsAPI.setInspectedTabId", &tab_id, nullptr, nullptr);
  
  auto* devtools = managed_web_contents()->GetDevToolsWebContents();
  bool has_window = devtools->GetUserData(NativeWindowRelay::UserDataKey());
  if (owner_window() && !has_window)
    handle->SetOwnerWindow(devtools, owner_window());
  Emit("devtools-opened");
}
void WebContents::DevToolsClosed() {
  v8::Locker locker(isolate());
  v8::HandleScope handle_scope(isolate());
  devtools_web_contents_.Reset();
  Emit("devtools-closed");
}
void WebContents::ShowAutofillPopup(content::RenderFrameHost* frame_host,