[GitHub] incubator-quickstep issue #341: Used MergeFrom instead of CopyFrom.

[zuyu]

Github user zuyu commented on the issue:

    https://github.com/apache/incubator-quickstep/pull/341
  
    `CopyFrom` = `Clear` + `MergeFrom`.
    
    Since we set a value for each new `proto`, we do not need `Clear` to reset 
the memory.


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