Move RTCVideoSource to webrtc/api/objc.

BUG=
R=tkchin@webrtc.org

Review URL: https://codereview.webrtc.org/1546783002 .

Patch from Jon Hjelle <hjon@andyet.net>.

Cr-Original-Commit-Position: refs/heads/master@{#11325}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 065aacc2490478062fc8128799d4ce90f5c8bcd6
5 files changed