getConfigForProvider(providerId) {
    const providerConfigs = this.getProviderConfigs();
    for (let i = 0; i < providerConfigs.length; i++) {
      // Check if current option matches provider ID.
      if (providerConfigs[i]['providerId'] === providerId) {
        return providerConfigs[i];
      }
    }
    return null;
  }
@param {string} providerId The provider id whose sign in provider config
    is to be returned.
@return {?Config.ProviderConfig} The list of sign in provider configs for
    supported IdPs.