Remove the dependency of TransportChannel and TransportChannelImpl.

webrtc/p2p/base/dtlstransportinternal.h

 /*
  *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_P2P_BASE_DTLSTRANSPORTINTERNAL_H_
 #define WEBRTC_P2P_BASE_DTLSTRANSPORTINTERNAL_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "webrtc/base/sslstreamadapter.h"
 #include "webrtc/p2p/base/icetransportinternal.h"
 #include "webrtc/p2p/base/jseptransport.h"
 #include "webrtc/p2p/base/packettransportinterface.h"
 
 namespace cricket {
 
+enum PacketFlags {
+  PF_NORMAL = 0x00,       // A normal packet.
+  PF_SRTP_BYPASS = 0x01,  // An encrypted SRTP packet; bypass any additional
+                          // crypto provided by the transport (e.g. DTLS)
+};
+
 // DtlsTransportInternal is an internal interface that does DTLS.
 // Once the public interface is supported,
 // (https://www.w3.org/TR/webrtc/#rtcdtlstransport-interface)
 // the DtlsTransportInterface will be split from this class.
 class DtlsTransportInternal : public rtc::PacketTransportInterface {
  public:
   virtual ~DtlsTransportInternal() {}
 
   virtual DtlsTransportState dtls_state() const = 0;
 
@@ skipping 48 matching lines @@
 
   // Expose the underneath IceTransport.
   virtual IceTransportInternal* ice_transport() = 0;
 
   sigslot::signal2<DtlsTransportInternal*, DtlsTransportState> SignalDtlsState;
 
   // Emitted whenever the Dtls handshake failed on some transport channel.
   sigslot::signal1<rtc::SSLHandshakeError> SignalDtlsHandshakeError;
 
   // Debugging description of this transport.
-  std::string debug_name() const override {
+  const std::string debug_name() const override {

[Taylor Brandstetter, 2017/01/10 19:43:47]

Like I mentioned earlier, we can remove the "const" from the return value.

[Zhi Huang, 2017/01/12 20:04:12]

Done.

     return transport_name() + " " + std::to_string(component());
   }
 
+ protected:
+  DtlsTransportInternal() {}
+
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(DtlsTransportInternal);
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_DTLSTRANSPORTINTERNAL_H_