0f4b3731c3
Cleaning AudioConferenceMixer APIs to match Chromium style guide. Main changes: 1. change all mutable references to pointers 2. add const to all non-mutable references 3. add const to as many methods as possible BUG= R=andrew@webrtc.org Review URL: https://codereview.webrtc.org/1311733003 . Cr-Commit-Position: refs/heads/master@{#9821}