Created the DtlsSrtpTransport.

pc/dtlssrtptransport.h

+/*
+ *  Copyright 2017 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 PC_DTLSSRTPTRANSPORT_H_
+#define PC_DTLSSRTPTRANSPORT_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "p2p/base/dtlstransportinternal.h"
+#include "pc/srtptransport.h"
+
+namespace webrtc {
+
+// This class exports the keying materials from the DtlsTransport underneath and
+// sets the crypto keys for the wrapped SrtpTransport.
+class DtlsSrtpTransport : public RtpTransportInternal {
+ public:
+  explicit DtlsSrtpTransport(
+      std::unique_ptr<webrtc::SrtpTransport> srtp_transport);
+
+  bool SetupDtlsSrtp(bool rtcp);
+
+  // Set a P2P layer DtlsTransport for RTP DtlsSrtpTransport.
+  void SetRtpDtlsTransport(cricket::DtlsTransportInternal* dtls_transport) {
+    rtp_dtls_transport_ = dtls_transport;
+  }
+
+  // Set a P2P layer DtlsTransport for RTCP DtlsSrtpTransport.
+  void SetRtcpDtlsTransport(cricket::DtlsTransportInternal* dtls_transport) {
+    rtcp_dtls_transport_ = dtls_transport;
+  }
+  // Set the header extension ids that should be encrypted.
+  // This method doesn't immediately update the SRTP session with the new IDs,
+  // and you need to call SetupDtlsSrtp for that to happen.
+  void SetSendEncryptedHeaderExtensionIds(
+      const std::vector<int>& send_extension_ids);
+
+  void SetRecvEncryptedHeaderExtensionIds(
+      const std::vector<int>& recv_extension_ids);
+
+  cricket::DtlsTransportInternal* rtp_dtls_transport() {
+    return rtp_dtls_transport_;
+  }
+
+  cricket::DtlsTransportInternal* rtcp_dtls_transport() {
+    return rtcp_dtls_transport_;
+  }
+
+  // RtpTransportInternal overrides.
+  void SetRtcpMuxEnabled(bool enable) override;

[Taylor Brandstetter, 2017/09/27 23:54:48]

nit: I'd remove the newlines between all the override methods.

+
+  rtc::PacketTransportInternal* rtp_packet_transport() const override;
+
+  void SetRtpPacketTransport(rtc::PacketTransportInternal* rtp) override;
+
+  PacketTransportInterface* GetRtpPacketTransport() const override;
+
+  rtc::PacketTransportInternal* rtcp_packet_transport() const override;
+
+  void SetRtcpPacketTransport(rtc::PacketTransportInternal* rtcp) override;
+
+  PacketTransportInterface* GetRtcpPacketTransport() const override;
+
+  bool IsWritable(bool rtcp) const override;
+
+  bool SendRtpPacket(rtc::CopyOnWriteBuffer* packet,
+                     const rtc::PacketOptions& options,
+                     int flags) override;
+
+  bool SendRtcpPacket(rtc::CopyOnWriteBuffer* packet,
+                      const rtc::PacketOptions& options,
+                      int flags) override;
+
+  bool HandlesPayloadType(int payload_type) const override;
+
+  void AddHandledPayloadType(int payload_type) override;
+
+  bool IsActive() { return active_; }
+
+  void ResetParams();
+
+  RTCError SetParameters(const RtpTransportParameters& parameters) override;
+
+  RtpTransportParameters GetParameters() const override;
+
+  // TODO(zhihuang): Remove this when we remove RtpTransportAdapter.
+  RtpTransportAdapter* GetInternal() override { return nullptr; }
+
+ private:
+  void ConnectToSrtpTransport();
+
+  void OnPacketReceived(bool rtcp,
+                        rtc::CopyOnWriteBuffer* packet,
+                        const rtc::PacketTime& packet_time);
+
+  void OnReadyToSend(bool ready);
+
+  // DtlsSrtpTransport become active after the DTLS-SRTP keys are installed.
+  bool active_ = false;

[Taylor Brandstetter, 2017/09/27 23:54:48]

Is this ever different than srtp_transport_->IsActive()?

+  std::unique_ptr<SrtpTransport> srtp_transport_;
+  // Owned by the TransportController.
+  cricket::DtlsTransportInternal* rtp_dtls_transport_ = nullptr;
+  cricket::DtlsTransportInternal* rtcp_dtls_transport_ = nullptr;
+};
+
+}  // namespace webrtc
+
+#endif  // PC_DTLSSRTPTRANSPORT_H_