Introduce rtc::PacketTransportInterface and let cricket::TransportChannel inherit.

webrtc/p2p/base/p2ptransportchannel_unittest.cc

Index: webrtc/p2p/base/p2ptransportchannel_unittest.cc
diff --git a/webrtc/p2p/base/p2ptransportchannel_unittest.cc b/webrtc/p2p/base/p2ptransportchannel_unittest.cc
index 7e65b4baba93d22a4cac78b71b31705229006f04..2c1013366aef5a31381db5f597f8e97a47aef8f8 100644
--- a/webrtc/p2p/base/p2ptransportchannel_unittest.cc
+++ b/webrtc/p2p/base/p2ptransportchannel_unittest.cc
@@ -13,6 +13,7 @@
 
 #include "webrtc/api/fakemetricsobserver.h"
 #include "webrtc/p2p/base/fakeportallocator.h"
+#include "webrtc/p2p/base/packettransport.h"
 #include "webrtc/p2p/base/p2ptransportchannel.h"
 #include "webrtc/p2p/base/testrelayserver.h"
 #include "webrtc/p2p/base/teststunserver.h"
@@ -670,8 +671,8 @@ class P2PTransportChannelTestBase : public testing::Test,
     TestSendRecv();
   }
 
-  void OnReadyToSend(TransportChannel* ch) {
-    GetEndpoint(ch)->ready_to_send_ = true;
+  void OnReadyToSend(rtc::PacketTransport* pt) {
+    GetEndpoint(static_cast<TransportChannel*>(pt))->ready_to_send_ = true;
   }
 
   // We pass the candidates directly to the other side.
@@ -777,12 +778,13 @@ class P2PTransportChannelTestBase : public testing::Test,
       }
     }
   }
-  void OnReadPacket(TransportChannel* channel,
+  void OnReadPacket(rtc::PacketTransport* pt,
                     const char* data,
                     size_t len,
                     const rtc::PacketTime& packet_time,
                     int flags) {
-    std::list<std::string>& packets = GetPacketList(channel);
+    std::list<std::string>& packets =
+        GetPacketList(static_cast<TransportChannel*>(pt));
     packets.push_front(std::string(data, len));
   }
   void OnRoleConflict(TransportChannelImpl* channel) {
@@ -2909,7 +2911,7 @@ class P2PTransportChannelPingTest : public testing::Test,
     conn->OnReadPacket(buf.Data(), buf.Length(), rtc::CreatePacketTime(0));
   }
 
-  void OnReadyToSend(TransportChannel* channel) {
+  void OnReadyToSend(rtc::PacketTransport* pt) {
     channel_ready_to_send_ = true;
   }
   void OnChannelStateChanged(TransportChannelImpl* channel) {