presto-main/src/main/java/io/prestosql/dispatcher/QueuedStatementResource.java/QueuedStatementResource/getScheme
class QueuedStatementResource:    private static String getScheme(String xForwardedProto, @Context UriInfo uriInfo)
    {
        return isNullOrEmpty(xForwardedProto) ? uriInfo.getRequestUri().getScheme() : xForwardedProto;
    }