Implement the NackModule as part of the new jitter buffer.

webrtc/modules/video_coding/include/video_coding_defines.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_VIDEO_CODING_INCLUDE_VIDEO_CODING_DEFINES_H_
 #define WEBRTC_MODULES_VIDEO_CODING_INCLUDE_VIDEO_CODING_DEFINES_H_
 
+#include <vector>
+
 #include "webrtc/modules/include/module_common_types.h"
 #include "webrtc/typedefs.h"
 #include "webrtc/video_frame.h"
 
 namespace webrtc {
 
 // Error codes
 #define VCM_FRAME_NOT_READY 3
 #define VCM_REQUEST_SLI 2
 #define VCM_MISSING_CALLBACK 1
@@ skipping 129 matching lines @@
     return -1;
   }
 
  protected:
   virtual ~VCMFrameTypeCallback() {}
 };
 
 // Callback class used for telling the user about which packet sequence numbers
 // are currently
 // missing and need to be resent.
+// TODO(philipel): Deprecate VCMPacketRequestCallback
+//                 and use NackSender instead.
 class VCMPacketRequestCallback {
  public:
   virtual int32_t ResendPackets(const uint16_t* sequenceNumbers,
                                 uint16_t length) = 0;
 
  protected:
   virtual ~VCMPacketRequestCallback() {}
 };
 
+class NackSender {
+ public:
+  virtual void SendNack(const std::vector<uint16_t>& sequence_numbers) = 0;
+
+ protected:
+  virtual ~NackSender() {}
+};
+
+class KeyFrameRequestSender {
+ public:
+  virtual void RequestKeyFrame() = 0;
+
+ protected:
+  virtual ~KeyFrameRequestSender() {}
+};
+
 // Callback used to inform the user of the the desired resolution
 // as subscribed by Media Optimization (Quality Modes)
 class VCMQMSettingsCallback {
  public:
   virtual int32_t SetVideoQMSettings(const uint32_t frameRate,
                                      const uint32_t width,
                                      const uint32_t height) = 0;
 
   virtual void SetTargetFramerate(int frame_rate) = 0;
 
  protected:
   virtual ~VCMQMSettingsCallback() {}
 };
 
 // Callback class used for telling the user about the size (in time) of the
 // render buffer, that is the size in time of the complete continuous frames.
 class VCMRenderBufferSizeCallback {
  public:
   virtual void RenderBufferSizeMs(int buffer_size_ms) = 0;
 
  protected:
   virtual ~VCMRenderBufferSizeCallback() {}
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_VIDEO_CODING_INCLUDE_VIDEO_CODING_DEFINES_H_