Fix screenshare loopback target bitrate which isn't correctly configured

BUG=
R=pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/48539004

Cr-Original-Commit-Position: refs/heads/master@{#8760}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 09098dabd38d25311472477179156795b4b971b0
1 file changed