GitLab

+ Add deadbeef@ as owner.
+ Remove hellner@ as owner.

https://code.google.com/p/chromium/codesearch#chromium/src/third_party/libjingle/source/talk/app/webrtc/mediastreamsignaling.h&l=28

Review URL: https://codereview.chromium.org/1460933003

Cr-Commit-Position: refs/heads/master@{#360574}