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* Electron version: 1.7.0
* Operating system: macOS

### Expected behavior
Electron works with `--debug` or `-debug` argument

<!-- What do you think should happen? -->

### Actual behavior
Electron won't run with arguments above.

<!-- What actually happens? -->

### How to reproduce

I've tried the standalone .app and the npm modules:

- for standalone .app it shows an error and returns a non-zero
(with "IOVARendererID property not found" the welcome window appears and I've manually close it)
![image](https://cloud.githubusercontent.com/assets/3816900/25955449/e4d09a72-369b-11e7-894b-415231293022.png)

- for npm module it just won't start and no error returns
![image](https://cloud.githubusercontent.com/assets/3816900/25955695/84b36dee-369c-11e7-9d19-6014f13d9a50.png)


I can confirm the `--debug` works with previous versions including 1.6.9 beta

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atom/browser/atom_browser_main_parts.cc
js_env_->OnMessageLoopCreated();
  
  
  node_bindings_->PrepareMessageLoop();
  node_bindings_->RunMessageLoop();
#if defined(USE_X11)
  ui::TouchFactory::SetTouchDeviceListFromCommandLine();
#endif
  
  gc_timer_.Start(
      FROM_HERE, base::TimeDelta::FromMinutes(1),
      base::Bind(&v8::Isolate::LowMemoryNotification,
                 base::Unretained(js_env_->isolate())));
  content::WebUIControllerFactory::RegisterFactory(
      AtomWebUIControllerFactory::GetInstance());
  brightray::BrowserMainParts::PreMainMessageLoopRun();
  bridge_task_runner_->MessageLoopIsReady();
  bridge_task_runner_ = nullptr;
#if defined(USE_X11)
  libgtkui::GtkInitFromCommandLine(*base::CommandLine::ForCurrentProcess());
#endif
#if !defined(OS_MACOSX)
  
  Browser::Get()->WillFinishLaunching();
  std::unique_ptr<base::DictionaryValue> empty_info(new base::DictionaryValue);
  Browser::Get()->DidFinishLaunching(*empty_info);
#endif
}
bool AtomBrowserMainParts::MainMessageLoopRun(int* result_code) {