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 8303d2bcdba1acb25b5e740e5db8014ae26d1478..58e8bfbc453e3261cfca0d04e2978687d2b6fa43 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 {
 
@@ -242,6 +243,8 @@ 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,