Simplify registration of RTP-header extensions.

webrtc/modules/rtp_rtcp/include/rtp_rtcp.h

 /*
  *  Copyright (c) 2012 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_MODULES_RTP_RTCP_INCLUDE_RTP_RTCP_H_
 #define WEBRTC_MODULES_RTP_RTCP_INCLUDE_RTP_RTCP_H_
 
 #include <set>
+#include <string>
 #include <utility>
 #include <vector>
 
 #include "webrtc/modules/include/module.h"
 #include "webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h"
 
 namespace webrtc {
 // Forward declarations.
 class ReceiveStatistics;
 class RemoteBitrateEstimator;
 class RtpReceiver;
 class Transport;
 class RtcEventLog;
 
+RTPExtensionType StringToRtpExtensionType(const std::string& extension);
+
 namespace rtcp {
 class TransportFeedback;
 }
 
 class RtpRtcp : public Module {
  public:
   struct Configuration {
     Configuration();
 
    /*  id                   - Unique identifier of this RTP/RTCP module object
@@ skipping 606 matching lines @@
 
     /*
     *   send a request for a keyframe
     *
     *   return -1 on failure else 0
     */
     virtual int32_t RequestKeyFrame() = 0;
 };
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_RTP_RTCP_INCLUDE_RTP_RTCP_H_