Fixed issue with how MTU is calculated.

BUG=
R=holmer@google.com, stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2410004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@4976 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/video_engine/internal/video_send_stream.cc b/video_engine/internal/video_send_stream.cc
index a0a99e0..55921c2 100644
--- a/video_engine/internal/video_send_stream.cc
+++ b/video_engine/internal/video_send_stream.cc
@@ -166,8 +166,8 @@
   assert(network_ != NULL);
 
   network_->RegisterSendTransport(channel_, transport_adapter_);
-  network_->SetMTU(channel_, config_.rtp.max_packet_size +
-                   VideoSendStream::Config::kDefaultPacketOverheader);
+  // 28 to match packet overhead in ModuleRtpRtcpImpl.
+  network_->SetMTU(channel_, config_.rtp.max_packet_size + 28);
 
   if (config.encoder) {
     external_codec_ = ViEExternalCodec::GetInterface(video_engine);