Fix crash in pacer.

BUG=1731
R=niklas.enbom@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/1410006

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@3964 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/modules/pacing/paced_sender.cc b/modules/pacing/paced_sender.cc
index 6c9939b..3cee8e1 100644
--- a/modules/pacing/paced_sender.cc
+++ b/modules/pacing/paced_sender.cc
@@ -42,8 +42,9 @@
 
 void PacedSender::PacketList::pop_front() {
   PacedSender::Packet& packet = packet_list_.front();
+  uint16_t sequence_number = packet.sequence_number_;
   packet_list_.pop_front();
-  sequence_number_set_.erase(packet.sequence_number_);
+  sequence_number_set_.erase(sequence_number);
 }
 
 void PacedSender::PacketList::push_back(const PacedSender::Packet& packet) {