- Electron version: 1.3.6
- Operating system: Windows 7 x64
- Other: Microsoft Office 2013 (will make more sense in a bit)

`shell.openItem()` is a blocking call, it would be nice if it's async or has an async version to handle synchronous external application behavior.

Reproduce: 
Open a password-protected Microsoft Excel file, `shell.openItem()` will be blocking until the Password window is submitted or dismissed. Consequently Microsoft Word does not have this issue.

Related to #2761.

shell/common/api/atom_api_shell.cc
gin_helper::Arguments* args) {
  base::win::ShortcutOperation operation = base::win::SHORTCUT_CREATE_ALWAYS;
  args->GetNext(&operation);
  gin::Dictionary options = gin::Dictionary::CreateEmpty(args->isolate());
  if (!args->GetNext(&options)) {
    args->ThrowError();
    return false;
  }
  base::win::ShortcutProperties properties;
  base::FilePath path;
  base::string16 str;
  int index;
  if (options.Get("target", &path))
    properties.set_target(path);
  if (options.Get("cwd", &path))
    properties.set_working_dir(path);
  if (options.Get("args", &str))
    properties.set_arguments(str);
  if (options.Get("description", &str))
    properties.set_description(str);
  if (options.Get("icon", &path) && options.Get("iconIndex", &index))
    properties.set_icon(path, index);
  if (options.Get("appUserModelId", &str))
    properties.set_app_id(str);
  base::win::ScopedCOMInitializer com_initializer;
  return base::win::CreateOrUpdateShortcutLink(shortcut_path, properties,
                                               operation);
}
v8::Local<v8::Value> ReadShortcutLink(gin_helper::ErrorThrower thrower,