Summary: In table.cc, the code section that reads in BlockContent and then put it into a Block, appears at least 4 times. This is too much duplication. BlockReader is much shorter after the change and reads way better. D10077 attempted that for index block read. This is a complete cleanup.
Test Plan: make check; ./db_stress
Reviewers: dhruba, sheki
Reviewed By: dhruba
CC: leveldb
Differential Revision: https://reviews.facebook.net/D10527
49fbd5531b