Revert of Remove GetTransport() from TransportChannelImpl

webrtc/p2p/base/dtlstransport.h

Index: webrtc/p2p/base/dtlstransport.h
diff --git a/webrtc/p2p/base/dtlstransport.h b/webrtc/p2p/base/dtlstransport.h
index 276b05f786f265bf026f941fa32bb75a51fe130d..9f2903e1d7fbbe195d9101acaa8acbaa1472a6aa 100644
--- a/webrtc/p2p/base/dtlstransport.h
+++ b/webrtc/p2p/base/dtlstransport.h
@@ -199,7 +199,7 @@
 
   DtlsTransportChannelWrapper* CreateTransportChannel(int component) override {
     DtlsTransportChannelWrapper* channel = new DtlsTransportChannelWrapper(
-        Base::CreateTransportChannel(component));
+        this, Base::CreateTransportChannel(component));
     channel->SetSslMaxProtocolVersion(ssl_max_version_);
     return channel;
   }