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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
DCHECK(self_);
  return self_;
}
bool AtomBrowserMainParts::SetExitCode(int code) {
  if (!exit_code_)
    return false;
  *exit_code_ = code;
  return true;
}
int AtomBrowserMainParts::GetExitCode() {
  return exit_code_ != nullptr ? *exit_code_ : 0;
}
base::Closure AtomBrowserMainParts::RegisterDestructionCallback(
    const base::Closure& callback) {
  auto iter = destructors_.insert(destructors_.end(), callback);
  return base::Bind(&Erase<std::list<base::Closure>>, &destructors_, iter);
}
void AtomBrowserMainParts::PreEarlyInitialization() {
  brightray::BrowserMainParts::PreEarlyInitialization();
#if defined(OS_POSIX)
  HandleSIGCHLD();
#endif
}
void AtomBrowserMainParts::PostEarlyInitialization() {