A class to facilitate making diagnostics for a topic using a FrequencyStatus. The word "headerless" in the class name refers to the fact that it is mainly designed for use with messages that do not have a header, and that cannot therefore be checked using a TimeStampStatus.
Constructs a HeaderlessTopicDiagnostic. @param name The name of the topic that is being diagnosed. @param diag The diagnostic_updater that the CompositeDiagnosticTask should add itself to. @param freq The parameters for the FrequencyStatus class that will be computing statistics.