Add experimental simulcast screen content mode

webrtc/media/engine/simulcast.h

 /*
  *  Copyright (c) 2014 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_MEDIA_ENGINE_SIMULCAST_H_
 #define WEBRTC_MEDIA_ENGINE_SIMULCAST_H_
 
 #include <vector>
 
 #include "webrtc/base/basictypes.h"
 #include "webrtc/config.h"
 
 namespace cricket {
 struct StreamParams;
 
+// TODO(sprang): Remove this, as we're moving away from temporal layer mode.
 // Config for use with screen cast when temporal layers are enabled.
 struct ScreenshareLayerConfig {
  public:
   ScreenshareLayerConfig(int tl0_bitrate, int tl1_bitrate);
 
   // Bitrates, for temporal layers 0 and 1.
   int tl0_bitrate_kbps;
   int tl1_bitrate_kbps;
 
   static ScreenshareLayerConfig GetDefault();
 
   // Parse bitrate from group name on format "(tl0_bitrate)-(tl1_bitrate)",
   // eg. "100-1000" for the default rates.
   static bool FromFieldTrialGroup(const std::string& group,
                                   ScreenshareLayerConfig* config);
 };
 
 // TODO(pthatcher): Write unit tests just for these functions,
 // independent of WebrtcVideoEngine.
 
 int GetTotalMaxBitrateBps(const std::vector<webrtc::VideoStream>& streams);
 
 // Get the ssrcs of the SIM group from the stream params.
 void GetSimulcastSsrcs(const StreamParams& sp, std::vector<uint32_t>* ssrcs);
 
 // Get simulcast settings.
+// TODO(sprang): Remove default parameter when it's not longer referenced.
 std::vector<webrtc::VideoStream> GetSimulcastConfig(size_t max_streams,
                                                     int width,
                                                     int height,
                                                     int max_bitrate_bps,
                                                     int max_qp,
-                                                    int max_framerate);
+                                                    int max_framerate,
+                                                    bool is_screencast = false);
+
+bool UseSimulcastScreenshare();
 
 }  // namespace cricket
 
 #endif  // WEBRTC_MEDIA_ENGINE_SIMULCAST_H_