Add histogram stats for send delay for a sent video stream.

webrtc/video/vie_channel.cc

Index: webrtc/video/vie_channel.cc
diff --git a/webrtc/video/vie_channel.cc b/webrtc/video/vie_channel.cc
index 108d409ce44c9e7694428e45a96e3e8f4ec8cf2b..3484f8df826d43f253a1badb84b5378f0cbc60da 100644
--- a/webrtc/video/vie_channel.cc
+++ b/webrtc/video/vie_channel.cc
@@ -63,6 +63,7 @@ std::unique_ptr<RtpRtcp> CreateRtpRtcpModule(
   configuration.send_bitrate_observer = nullptr;
   configuration.send_frame_count_observer = nullptr;
   configuration.send_side_delay_observer = nullptr;
+  configuration.send_packet_observer = nullptr;
   configuration.bandwidth_callback = nullptr;
   configuration.transport_feedback_callback = nullptr;