code: public B preflightResponseHeader(CharSequence name, Object... values) {
          requireNonNull(name, "name");
          requireNonNull(values, "values");
          checkArgument(values.length > 0, "values should not be empty.");
          for (int i = 0; i < values.length; i++) {
              if (values[i] == null) {
                  throw new NullPointerException("values[" + i + ']');
              }
          }
          preflightResponseHeaders.put(HttpHeaderNames.of(name),
                                       new ConstantValueSupplier(ImmutableList.copyOf(values)));
          return self();
      }
docs: Specifies HTTP response headers that should be added to a CORS preflight response.
  
  <p>An intermediary like a load balancer might require that a CORS preflight request
  have certain headers set. This enables such headers to be added.
  
  @param name the name of the HTTP header.
  @param values the values for the HTTP header.
  @return {@code this} to support method chaining.