Major Description
In SOLR-3215 we started cloning documents before adding them locally and send the cloned copy to replicas. This was done because processors after DistributedUpdateProcessor can affect the docs before they are sent to the replicas.
However, we can avoid the deep copy if we know for sure that the processors after DUP are one of (LogUpdateProcessor, RunUpdateProcessor, TolerantUpdateProcessor) which definitely do not modify the document. This ensures that the common case is optimized.