Review Request: Improved Duration << operator to 1) handle negative durations; 2) try to find a whole number to print out.

[Jiang Yan Xu]

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https://reviews.apache.org/r/11331/
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Review request for mesos, Benjamin Hindman and Vinod Kone.


Description
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- Currently when the result isn't a whole number, we go one-level down in terms 
of the unit of time and see if we can get a whole number there. If so, use the 
lower unit; if not, use the higher unit.


This addresses bug MESOS-477.
    https://issues.apache.org/jira/browse/MESOS-477


Diffs
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  third_party/libprocess/third_party/stout/include/stout/duration.hpp 
c943ab196871cf4c55f2a2dce5ef85ffe3a22577 
  third_party/libprocess/third_party/stout/tests/duration_tests.cpp 
421615aa510f540ccfc0413d3252bbdedd70f7da 

Diff: https://reviews.apache.org/r/11331/diff/


Testing
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make check


Thanks,

Jiang Yan Xu