Work on flexible mode and screen sharing.

webrtc/modules/video_coding/main/source/generic_encoder.cc

Index: webrtc/modules/video_coding/main/source/generic_encoder.cc
diff --git a/webrtc/modules/video_coding/main/source/generic_encoder.cc b/webrtc/modules/video_coding/main/source/generic_encoder.cc
index de196040f053df77ebfd7753ce038a1a52ff42db..c10c3ab9a59dc2fbc7c84dcbff977babe4bb7567 100644
--- a/webrtc/modules/video_coding/main/source/generic_encoder.cc
+++ b/webrtc/modules/video_coding/main/source/generic_encoder.cc
@@ -54,11 +54,9 @@ void CopyCodecSpecific(const CodecSpecificInfo* info, RTPVideoHeader* rtp) {
       rtp->codecHeader.VP9.inter_layer_predicted =
           info->codecSpecific.VP9.inter_layer_predicted;
       rtp->codecHeader.VP9.gof_idx = info->codecSpecific.VP9.gof_idx;
-
-      // Packetizer needs to know the number of spatial layers to correctly set
-      // the marker bit, even when the number won't be written in the packet.
       rtp->codecHeader.VP9.num_spatial_layers =
           info->codecSpecific.VP9.num_spatial_layers;
+
       if (info->codecSpecific.VP9.ss_data_available) {
         rtp->codecHeader.VP9.spatial_layer_resolution_present =
             info->codecSpecific.VP9.spatial_layer_resolution_present;
@@ -71,6 +69,10 @@ void CopyCodecSpecific(const CodecSpecificInfo* info, RTPVideoHeader* rtp) {
         }
         rtp->codecHeader.VP9.gof.CopyGofInfoVP9(info->codecSpecific.VP9.gof);
       }
+
+      rtp->codecHeader.VP9.num_ref_pics = info->codecSpecific.VP9.num_ref_pics;
+      for (int i = 0; i < info->codecSpecific.VP9.num_ref_pics; ++i)
+        rtp->codecHeader.VP9.pid_diff[i] = info->codecSpecific.VP9.p_diff[i];
       return;
     }
     case kVideoCodecH264: