Remove BaseChannel's dependency on TransportController.

webrtc/p2p/base/transportcontroller.h

Index: webrtc/p2p/base/transportcontroller.h
diff --git a/webrtc/p2p/base/transportcontroller.h b/webrtc/p2p/base/transportcontroller.h
index a46ce00dbc329a8f4627cca1318d06139572a476..cc925dc2d6f3d611f6468e0f5cbb2c277324bb26 100644
--- a/webrtc/p2p/base/transportcontroller.h
+++ b/webrtc/p2p/base/transportcontroller.h
@@ -113,12 +113,16 @@ class TransportController : public sigslot::has_slots<>,
 
   // Creates a channel if it doesn't exist. Otherwise, increments a reference
   // count and returns an existing channel.
+  TransportChannel* CreateTransportChannel(const std::string& transport_name,

[Taylor Brandstetter, 2017/01/09 22:50:42]

If EnableBundle were called on the networking thread, we could avoid the
signaling thread versions of these methods.

[Zhi Huang, 2017/01/12 03:47:46]

This method could be called on other threads in WebRtcSession.

+                                           int component);
   virtual TransportChannel* CreateTransportChannel_n(
       const std::string& transport_name,
       int component);
 
   // Decrements a channel's reference count, and destroys the channel if
   // nothing is referencing it.
+  void DestroyTransportChannel(const std::string& transport_name,
+                               int component);
   virtual void DestroyTransportChannel_n(const std::string& transport_name,
                                          int component);