Initialize output_will_be_muted_.
Initialize output_will_be_muted_.

TBR=aluebs

Review URL: https://webrtc-codereview.appspot.com/8659004

Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 38bf249049a16233904c8617edaf0f0b6155d9a2

sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc