Revert of Refactoring that removes P2PTransport and DtlsTransport classes.

webrtc/p2p/base/p2ptransportchannel.cc

Index: webrtc/p2p/base/p2ptransportchannel.cc
diff --git a/webrtc/p2p/base/p2ptransportchannel.cc b/webrtc/p2p/base/p2ptransportchannel.cc
index 5f858c4858f952174b878891a875648bbd69de43..e1a955c69611f21321ea5fa35772666e7fa45aae 100644
--- a/webrtc/p2p/base/p2ptransportchannel.cc
+++ b/webrtc/p2p/base/p2ptransportchannel.cc
@@ -96,6 +96,12 @@
 
 static constexpr int a_is_better = 1;
 static constexpr int b_is_better = -1;
+
+P2PTransportChannel::P2PTransportChannel(const std::string& transport_name,
+                                         int component,
+                                         P2PTransport* transport,
+                                         PortAllocator* allocator)
+    : P2PTransportChannel(transport_name, component, allocator) {}
 
 P2PTransportChannel::P2PTransportChannel(const std::string& transport_name,
                                          int component,