Wire up transport sequence number / send time callbacks to webrtc via libjingle.

talk/media/base/constants.cc

Index: talk/media/base/constants.cc
diff --git a/talk/media/base/constants.cc b/talk/media/base/constants.cc
index 0d0a33c18aad2bcc58b6c3a2207f0097a6c9da44..40630049681d769bc1ffdc302a00bd12fb019db7 100644
--- a/talk/media/base/constants.cc
+++ b/talk/media/base/constants.cc
@@ -124,6 +124,10 @@ const char kRtpVideoRotationHeaderExtension[] = "urn:3gpp:video-orientation";
 const char kRtpVideoRotation6BitsHeaderExtensionForTesting[] =
     "urn:3gpp:video-orientation:6";
 
+const int kRtpTransportSequenceNumberHeaderExtensionDefaultId = 5;
+const char kRtpTransportSequenceNumberHeaderExtension[] =
+    "http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions";
+
 const int kNumDefaultUnsignalledVideoRecvStreams = 0;
 
 const char kVp8CodecName[] = "VP8";