#include <FWCore/Framework/interface/MessageForSource.h>
Description: Information passed from controller to source when doing multicore processing
Usage: This class is an internal detail of how the parent process communicates to child processes. It is used with the posix message queue to send what events child processes should handle. The events are designated as a 'block' where we give the index to the first event in the block and then the number of consecutive events to process in the block.
NOTE: If the number of consecutive events (i.e. nIndices) is 0, this means there is no more work to do and the child process should end.