Remove old_factory from WebRtcVideoEngine.
Remove old_factory from WebRtcVideoEngine.

Minor pending cleanup.

R=pthatcher@webrtc.org
BUG=

Review URL: https://webrtc-codereview.appspot.com/28239004

Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 13518951e37775dd73de0c5661726db08e83cb8c

sippet/talk,sippet/talk,sippet/talk,sippet/talk,sippet/talk