code: function WebIdentityCredentials(params, clientConfig) {
      AWS.Credentials.call(this);
      this.expired = true;
      this.params = params;
      this.params.RoleSessionName = this.params.RoleSessionName || 'web-identity';
      this.data = null;
      this._clientConfig = AWS.util.copy(clientConfig || {});
    }
docs: Creates a new credentials object.
  @param (see AWS.STS.assumeRoleWithWebIdentity)
  @example Creating a new credentials object
  AWS.config.credentials = new AWS.WebIdentityCredentials({
  RoleArn: 'arn:aws:iam::1234567890:role/WebIdentity',
  WebIdentityToken: 'ABCDEFGHIJKLMNOP', // token from identity service
  RoleSessionName: 'web' // optional name, defaults to web-identity
  }, {
  // optionally provide configuration to apply to the underlying AWS.STS service client
  // if configuration is not provided, then configuration will be pulled from AWS.config
  
  // specify timeout options
  httpOptions: {
  timeout: 100
  }
  });
  @see AWS.STS.assumeRoleWithWebIdentity
  @see AWS.Config