Pulls the audio handling out of copresence and into its own component, with no functional changes. This is part of a larger plan to make audio token exchange available directly, via a private API.

rkc@ and xiyuan@ for copresence review.
caitkp@ for component review.
thestig@ for chrome/browser/DEPS review.
jam@, avi@ for content/ DEPS review.
dalecurtis@ for media/ DEPS review.
andrew@webrtc for WavWriter DEPS review.

BUG=455823

Review URL: https://codereview.chromium.org/865483005

Cr-Commit-Position: refs/heads/master@{#316639}
62 files changed