Add ramp-up tests for transport sequence number with and w/o audio.

webrtc/test/fake_network_pipe.cc

Index: webrtc/test/fake_network_pipe.cc
diff --git a/webrtc/test/fake_network_pipe.cc b/webrtc/test/fake_network_pipe.cc
index 4e431222dac108bafcfc8dc4003c4c08b688d3d1..491a0526b9b39b991370be8616d4abe005b754ea 100644
--- a/webrtc/test/fake_network_pipe.cc
+++ b/webrtc/test/fake_network_pipe.cc
@@ -146,7 +146,8 @@ int FakeNetworkPipe::AverageDelay() {
   if (sent_packets_ == 0)
     return 0;
 
-  return total_packet_delay_ / static_cast<int>(sent_packets_);
+  return static_cast<int>(total_packet_delay_ /
+                          static_cast<int64_t>(sent_packets_));
 }
 
 void FakeNetworkPipe::Process() {