Summary:
This diff improves the documentation for GetOptionsFromMap APIs and
fixes a bug in GetOptionsFromMap functions in convenience.h
where new_options will still be changed when the function
call is not successful.
Test Plan: options_test
Reviewers: IslamAbdelRahman, kradhakrishnan, andrewkr, sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D61731
6056d6317d