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 d4ff1daeb4e215d1f328d18a5377812adeeb6778..a4c82f3ecf79de557a9466361bb24276189362d5 100644
--- a/content/browser/renderer_host/p2p/socket_host.h
+++ b/content/browser/renderer_host/p2p/socket_host.h
@@ -25,6 +25,28 @@ struct PacketOptions;
 namespace content {
 class P2PMessageThrottler;
 
+namespace packet_processing_helpers {
+
+// This method can handle only RTP packet, otherwise this method must not be
+// called. It will try to do, 1. update absolute send time extension header
+// if present with current time and 2. update HMAC in RTP packet.
+// If abs_send_time is 0, ApplyPacketOption will get current time from system.
+CONTENT_EXPORT bool ApplyPacketOptions(char* data, int length,
+                                       const talk_base::PacketOptions& options,
+                                       uint32 abs_send_time);
+
+// Helper method which finds RTP ofset and length if the packet is encapsulated
+// in a TURN Channel Message or TURN Send Indication message.
+CONTENT_EXPORT bool GetRtpPacketStartPositionAndLength(char* data, int length,
+                                                       int* rtp_start_pos,
+                                                       int* rtp_packet_length);
+// Helper method which updates absoulute send time extension if present.
+CONTENT_EXPORT bool UpdateRtpAbsSendTimeExtn(char* rtp, int length,
+                                             int extension_id,
+                                             uint32 abs_send_time);
+
+}  // packet_processing_helpers
+
 // Base class for P2P sockets.
 class CONTENT_EXPORT P2PSocketHost {
  public: