Revert of Completed the functionalities of SrtpTransport.

p2p/base/fakepackettransport.h

Index: p2p/base/fakepackettransport.h
diff --git a/p2p/base/fakepackettransport.h b/p2p/base/fakepackettransport.h
index 2af14c1bda2ff10e9bb613635fb59f9da9544888..654d05bcec80c54af0d3c9a3f1692d1b9fba33be 100644
--- a/p2p/base/fakepackettransport.h
+++ b/p2p/base/fakepackettransport.h
@@ -86,8 +86,6 @@ class FakePacketTransport : public PacketTransportInternal {
   bool GetOption(Socket::Option opt, int* value) override { return true; }
   int GetError() override { return 0; }
 
-  const CopyOnWriteBuffer* last_sent_packet() { return &last_sent_packet_; }
-
  private:
   void set_writable(bool writable) {
     if (writable_ == writable) {
@@ -109,14 +107,12 @@ class FakePacketTransport : public PacketTransportInternal {
   }
 
   void SendPacketInternal(const CopyOnWriteBuffer& packet) {
-    last_sent_packet_ = packet;
     if (dest_) {
       dest_->SignalReadPacket(dest_, packet.data<char>(), packet.size(),
                               CreatePacketTime(0), 0);
     }
   }
 
-  CopyOnWriteBuffer last_sent_packet_;
   AsyncInvoker invoker_;
   std::string debug_name_;
   FakePacketTransport* dest_ = nullptr;