This CL adds methods to manipulate RTP header extension, particularly

content/browser/renderer_host/p2p/socket_host_udp.cc

Index: content/browser/renderer_host/p2p/socket_host_udp.cc
diff --git a/content/browser/renderer_host/p2p/socket_host_udp.cc b/content/browser/renderer_host/p2p/socket_host_udp.cc
index 921eac857365bea874c98001e053baac5a184a8f..59edac024c4b325f4fe50f28c5bc2657d11a645a 100644
--- a/content/browser/renderer_host/p2p/socket_host_udp.cc
+++ b/content/browser/renderer_host/p2p/socket_host_udp.cc
@@ -15,6 +15,7 @@
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
 #include "net/base/net_util.h"
+#include "third_party/libjingle/source/talk/base/asyncpacketsocket.h"
 
 namespace {
 
@@ -234,6 +235,8 @@ void P2PSocketHostUdp::DoSend(const PendingPacket& packet) {
       last_dscp_ = net::DSCP_NO_CHANGE;
     }
   }
+  talk_base::PacketOptions options;
+  MaybeUpdateRtpSendTimeExtn(packet.data->data(), packet.size, options);
   int result = socket_->SendTo(
       packet.data.get(),
       packet.size,