[yt-dev] [yt_analysis/yt] _identify_base_chunk for Octree codes should not pre-allocate a mask (issue #553)

[Matthew Turk]

New issue 553: _identify_base_chunk for Octree codes should not pre-allocate a mask
https://bitbucket.org/yt_analysis/yt/issue/553/_identify_base_chunk-for-octree-codes

Matthew Turk:

The mask for child octs should not be allocated during the course of `_identify_base_chunk` if it can at all be avoided.  This is costly.

Responsible: MatthewTurk