Thinning out the Transport class.

Connecting TransportChannelImpls directly to the TransportController,
and removing redundant signal forwarding/state aggregating code from
Transport. This brings us closer to just getting rid of Transport
entirely.

R=pthatcher@webrtc.org

Review URL: https://codereview.webrtc.org/1380563002 .

Cr-Original-Commit-Position: refs/heads/master@{#10120}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: c4d3a5d44c25fb42c26393b6ddc0feadd52e5e2f
6 files changed