Remove MediaChannel::SetRemoteRenderer().

Remove MediaChannel::SetRemoteRenderer().
This is following discussion in: https://codereview.webrtc.org/1385893002/diff/60001/talk/media/webrtc/webrtcvoiceengine.cc#newcode2410

BUG=webrtc:4690
Committed: https://crrev.com/d4cec0d8fa7913bc9dfa9137e44cca9098e16698
Cr-Commit-Position: refs/heads/master@{#10237}

[the sun, 2015-10-09 08:26:51]

solenberg@webrtc.org changed reviewers:
+ tommi@webrtc.org

[the sun, 2015-10-09 14:24:52]

solenberg@webrtc.org changed reviewers:
+ pthatcher@webrtc.org

[the sun, 2015-10-09 14:25:29]

solenberg@webrtc.org changed reviewers:
- tommi@webrtc.org

[tommi, 2015-10-09 14:33:46]

tommi@webrtc.org changed reviewers:
+ tommi@webrtc.org

[tommi, 2015-10-09 14:33:46]

lgtm

[the sun, 2015-10-09 14:40:16]

solenberg@webrtc.org changed reviewers:
- pthatcher@webrtc.org

[the sun, 2015-10-09 14:46:59]

The CQ bit was checked by solenberg@webrtc.org

[the sun, 2015-10-09 14:46:59]

The patchset sent to the CQ was uploaded after l-g-t-m from tommi@webrtc.org
Link to the patchset: https://codereview.webrtc.org/1398823003/#ps60001 (title:
"rebase")

[commit-bot: I haz the power, 2015-10-09 14:47:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1398823003/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1398823003/60001

[commit-bot: I haz the power, 2015-10-09 15:55:52]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-10-09 15:56:02]

Patchset 4 (id:??) landed as
https://crrev.com/d4cec0d8fa7913bc9dfa9137e44cca9098e16698
Cr-Commit-Position: refs/heads/master@{#10237}