minyue 84db6fa7f5 Adding BlockMeanCalculator for AEC.
This will improve the readability of AEC code.

BUG=

Review URL: https://codereview.webrtc.org/1805633006

Cr-Commit-Position: refs/heads/master@{#12123}
2016-03-24 21:36:33 +00:00
..
2014-07-10 07:53:13 +00:00
2015-05-20 05:20:04 +00:00