Injectable audio encoders: voice_engine/channel changes.

Adds a SetEncoder call to voe::Channel, so that we can move encoder setup outside of Voice Engine.

BUG=webrtc:5806

Review-Url: https://codereview.webrtc.org/2703373006
Cr-Original-Commit-Position: refs/heads/master@{#17572}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 1ffbd6c93cf322de23b3772c39021c58abe4b7bc
6 files changed