* 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
GoToOffset(offset);
  return false;
}
void WebContents::FindReply(content::WebContents* web_contents,
                            int request_id,
                            int number_of_matches,
                            const gfx::Rect& selection_rect,
                            int active_match_ordinal,
                            bool final_update) {
  if (!final_update)
    return;
  v8::Locker locker(isolate());
  v8::HandleScope handle_scope(isolate());
  mate::Dictionary result = mate::Dictionary::CreateEmpty(isolate());
  result.Set("requestId", request_id);
  result.Set("matches", number_of_matches);
  result.Set("selectionArea", selection_rect);
  result.Set("activeMatchOrdinal", active_match_ordinal);
  result.Set("finalUpdate", final_update);  
  Emit("found-in-page", result);
}
bool WebContents::CheckMediaAccessPermission(