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

webrtc/p2p/base/packettransportinterface.h

Index: webrtc/p2p/base/packettransportinterface.h
diff --git a/webrtc/p2p/base/packettransportinterface.h b/webrtc/p2p/base/packettransportinterface.h
new file mode 100644
index 0000000000000000000000000000000000000000..401ffb62b45c3d5b3181fc42dccfc9518f3afad1
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+++ b/webrtc/p2p/base/packettransportinterface.h
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+/*
+ *  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_PACKETTRANSPORTINTERFACE_H_
+#define WEBRTC_P2P_BASE_PACKETTRANSPORTINTERFACE_H_
+
+#include <string>
+#include <vector>
+
+#include "webrtc/base/sigslot.h"
+
+namespace rtc {
+struct PacketOptions;
+struct PacketTime;
+
+struct PacketTransportInterface : public sigslot::has_slots<> {
+  virtual ~PacketTransportInterface() {}
+  virtual const std::string debug_name() const = 0;
+  virtual bool writable() const = 0;
+
+  // Attempts to send the given packet.  The return value is < 0 on failure.
+  // TODO(johan): Remove the default argument once channel code is updated.
+  virtual int SendPacket(const char* data,
+                         size_t len,
+                         const rtc::PacketOptions& options,
+                         int flags = 0) = 0;
+
+  // Sets a socket option. Note that not all options are
+  // supported by all transport types.
+  virtual int SetOption(rtc::Socket::Option opt, int value) = 0;
+
+  // TODO(pthatcher): Once Chrome's MockPacketTransportInterface implments
+  // this, remove the default implementation.
+  virtual bool GetOption(rtc::Socket::Option opt, int* value) { return false; }
+
+  // Returns the most recent error that occurred on this channel.
+  virtual int GetError() = 0;
+
+  sigslot::signal1<PacketTransportInterface*> SignalWritableState;
+
+  // Emitted when the PacketTransportInterface's ability to send has changed.
+  sigslot::signal1<PacketTransportInterface*> SignalReadyToSend;
+
+  // Signalled each time a packet is received on this channel.
+  sigslot::signal5<PacketTransportInterface*,
+                   const char*,
+                   size_t,
+                   const rtc::PacketTime&,
+                   int>
+      SignalReadPacket;
+
+  // Signalled each time a packet is sent on this channel.
+  sigslot::signal2<PacketTransportInterface*, const rtc::SentPacket&>
+      SignalSentPacket;
+};
+
+}  // namespace rtc
+
+#endif  // WEBRTC_P2P_BASE_PACKETTRANSPORTINTERFACE_H_