Reason for revert:
Didn't intend to land yet. Chromium CL still needed.
Original issue's description:
> Add virtual Initialize methods to PortAllocator and NetworkManager.
>
> This will allow PeerConnection to handle hopping to the right thread
> and doing thread-specific initialization for the PortAllocator.
> This eliminates a required thread-hop for whatever is passing the
> PortAllocator into CreatePeerConnection.
>
> BUG=617648
> R=pthatcher@webrtc.org, skvlad@webrtc.org
>
> Committed: https://crrev.com/a6bdb0990a659ff9e7c4374f5033a6bcc4fbfb21
> Cr-Commit-Position: refs/heads/master@{#13283}
TBR=pthatcher@webrtc.org,skvlad@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=617648
Review-Url: https://codereview.webrtc.org/2092023004
Cr-Commit-Position: refs/heads/master@{#13284}
ba8d4337b7