Make PacketTransportInternal inherit from PacketTransportInterface.

webrtc/p2p/base/fakepackettransport.h

Index: webrtc/p2p/base/fakepackettransport.h
diff --git a/webrtc/p2p/base/fakepackettransport.h b/webrtc/p2p/base/fakepackettransport.h
index 7e2f08437ec9782164e70d1007e9fcc15d749117..64e0f7d5a828fa2763a1d587d18e5ef2ad5ec792 100644
--- a/webrtc/p2p/base/fakepackettransport.h
+++ b/webrtc/p2p/base/fakepackettransport.h
@@ -21,8 +21,7 @@
 namespace rtc {
 
 // Used to simulate a packet-based transport.
-class FakePacketTransport : public PacketTransportInternal,
-                            public webrtc::PacketTransportInterface {
+class FakePacketTransport : public PacketTransportInternal {
  public:
   explicit FakePacketTransport(const std::string& debug_name)
       : debug_name_(debug_name) {}
@@ -87,9 +86,6 @@ class FakePacketTransport : public PacketTransportInternal,
   bool GetOption(Socket::Option opt, int* value) override { return true; }
   int GetError() override { return 0; }
 
- protected:
-  PacketTransportInternal* GetInternal() override { return this; }
-
  private:
   void set_writable(bool writable) {
     if (writable_ == writable) {