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diff --git a/third_party/libwebrtc/pc/rtcp_mux_filter.h b/third_party/libwebrtc/pc/rtcp_mux_filter.h
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+/*
+ *  Copyright 2004 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_RTCP_MUX_FILTER_H_
+#define PC_RTCP_MUX_FILTER_H_
+
+#include "pc/session_description.h"
+
+namespace cricket {
+
+// RTCP Muxer, as defined in RFC 5761 (http://tools.ietf.org/html/rfc5761)
+class RtcpMuxFilter {
+ public:
+  RtcpMuxFilter();
+
+  // Whether RTCP mux has been negotiated with a final answer (not provisional).
+  bool IsFullyActive() const;
+
+  // Whether RTCP mux has been negotiated with a provisional answer; this means
+  // a later answer could disable RTCP mux, and so the RTCP transport should
+  // not be disposed yet.
+  bool IsProvisionallyActive() const;
+
+  // Whether the filter is active, i.e. has RTCP mux been properly negotiated,
+  // either with a final or provisional answer.
+  bool IsActive() const;
+
+  // Make the filter active (fully, not provisionally) regardless of the
+  // current state. This should be used when an endpoint *requires* RTCP mux.
+  void SetActive();
+
+  // Specifies whether the offer indicates the use of RTCP mux.
+  bool SetOffer(bool offer_enable, ContentSource src);
+
+  // Specifies whether the provisional answer indicates the use of RTCP mux.
+  bool SetProvisionalAnswer(bool answer_enable, ContentSource src);
+
+  // Specifies whether the answer indicates the use of RTCP mux.
+  bool SetAnswer(bool answer_enable, ContentSource src);
+
+ private:
+  bool ExpectOffer(bool offer_enable, ContentSource source);
+  bool ExpectAnswer(ContentSource source);
+  enum State {
+    // RTCP mux filter unused.
+    ST_INIT,
+    // Offer with RTCP mux enabled received.
+    // RTCP mux filter is not active.
+    ST_RECEIVEDOFFER,
+    // Offer with RTCP mux enabled sent.
+    // RTCP mux filter can demux incoming packets but is not active.
+    ST_SENTOFFER,
+    // RTCP mux filter is active but the sent answer is only provisional.
+    // When the final answer is set, the state transitions to ST_ACTIVE or
+    // ST_INIT.
+    ST_SENTPRANSWER,
+    // RTCP mux filter is active but the received answer is only provisional.
+    // When the final answer is set, the state transitions to ST_ACTIVE or
+    // ST_INIT.
+    ST_RECEIVEDPRANSWER,
+    // Offer and answer set, RTCP mux enabled. It is not possible to de-activate
+    // the filter.
+    ST_ACTIVE
+  };
+  State state_;
+  bool offer_enable_;
+};
+
+}  // namespace cricket
+
+#endif  // PC_RTCP_MUX_FILTER_H_