Add placeholder files for talk/app/webrtc/mediacontroller.cc/.h to be able to update Chrome's libji…

Add placeholder files for talk/app/webrtc/mediacontroller.cc/.h to be able to update Chrome's libjingle.gyp before the MediaController implementation CL is submitted.

BUG=webrtc:4690
Committed: https://crrev.com/7b38f6937087fed7011818a2692cd7f55c580813
Cr-Commit-Position: refs/heads/master@{#9872}

[the sun, 2015-09-03 15:08:14]

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

[pthatcher1, 2015-09-04 23:04:17]

lgtm

[the sun, 2015-09-07 10:19:06]

The CQ bit was checked by solenberg@webrtc.org

[the sun, 2015-09-07 10:19:07]

The patchset sent to the CQ was uploaded after l-g-t-m from pthatcher@webrtc.org
Link to the patchset: https://codereview.webrtc.org/1308543007/#ps20001 (title:
"rebase")

[commit-bot: I haz the power, 2015-09-07 10:19:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1308543007/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1308543007/20001

[commit-bot: I haz the power, 2015-09-07 11:38:37]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-09-07 11:38:48]

Patchset 2 (id:??) landed as
https://crrev.com/7b38f6937087fed7011818a2692cd7f55c580813
Cr-Commit-Position: refs/heads/master@{#9872}