This CL adds methods to manipulate RTP header extension, particularly

content/browser/renderer_host/p2p/socket_host.h

Index: content/browser/renderer_host/p2p/socket_host.h
diff --git a/content/browser/renderer_host/p2p/socket_host.h b/content/browser/renderer_host/p2p/socket_host.h
index 40dc713fa454a89c0274dfe04bcf3a059400efb5..b7f71ef8d25bf21a3e8dfa9008452e1b0b84037e 100644
--- a/content/browser/renderer_host/p2p/socket_host.h
+++ b/content/browser/renderer_host/p2p/socket_host.h
@@ -18,6 +18,10 @@ namespace net {
 class URLRequestContextGetter;
 }
 
+namespace talk_base {
+struct PacketOptions;
+}
+
 namespace content {
 class P2PMessageThrottler;
 
@@ -49,6 +53,9 @@ class CONTENT_EXPORT P2PSocketHost {
   virtual bool SetOption(P2PSocketOption option, int value) = 0;
 
  protected:
+  void MaybeUpdateRtpSendTimeExtn(char* data, int length,
+                                  const talk_base::PacketOptions& options);
+
   friend class P2PSocketHostTcpTestBase;
 
   // TODO(mallinath) - Remove this below enum and use one defined in
@@ -93,6 +100,13 @@ class CONTENT_EXPORT P2PSocketHost {
                                 StunMessageType* type);
   static bool IsRequestOrResponse(StunMessageType type);
 
+  bool FindAndUpdateRtpAbsSendTimeExtension(
+      char* data, int len, const talk_base::PacketOptions& options);
+  void UpdateRtpAbsSendTimeExtension(char* data, int len);
+
+  void UpdateHmac(char* packet, int len,
+                  const talk_base::PacketOptions& options);
+
   IPC::Sender* message_sender_;
   int id_;
   State state_;