function ChromeExOAuth(url_request_token, url_auth_token, url_access_token,
                       consumer_key, consumer_secret, oauth_scope, opt_args) {
  this.url_request_token = url_request_token;
  this.url_auth_token = url_auth_token;
  this.url_access_token = url_access_token;
  this.consumer_key = consumer_key;
  this.consumer_secret = consumer_secret;
  this.oauth_scope = oauth_scope;
  this.app_name = opt_args && opt_args['app_name'] ||
      "ChromeExOAuth Library";
  this.key_token = "oauth_token";
  this.key_token_secret = "oauth_token_secret";
  this.callback_page = opt_args && opt_args['callback_page'] ||
      "chrome_ex_oauth.html";
  this.auth_params = {};
  if (opt_args && opt_args['auth_params']) {
    for (key in opt_args['auth_params']) {
      if (opt_args['auth_params'].hasOwnProperty(key)) {
        this.auth_params[key] = opt_args['auth_params'][key];
      }
    }
  }
}
Constructor - no need to invoke directly, call initBackgroundPage instead.
@constructor
@param {String} url_request_token The OAuth request token URL.
@param {String} url_auth_token The OAuth authorize token URL.
@param {String} url_access_token The OAuth access token URL.
@param {String} consumer_key The OAuth consumer key.
@param {String} consumer_secret The OAuth consumer secret.
@param {String} oauth_scope The OAuth scope parameter.
@param {Object} opt_args Optional arguments.  Recognized parameters:
    "app_name" {String} Name of the current application
    "callback_page" {String} If you renamed chrome_ex_oauth.html, the name
         this file was renamed to.