Adding the ability to create an RtpSender without a track.

webrtc/base/helpers.h

Index: webrtc/base/helpers.h
diff --git a/webrtc/base/helpers.h b/webrtc/base/helpers.h
index 102c08bd0dbc6150070326700073dd051da5fca3..0e7937362a334c7cc29bc9a3ff203c1f7fec647c 100644
--- a/webrtc/base/helpers.h
+++ b/webrtc/base/helpers.h
@@ -39,6 +39,9 @@ bool CreateRandomString(size_t length, std::string* str);
 bool CreateRandomString(size_t length, const std::string& table,
                         std::string* str);
 
+// Generates a (cryptographically) random UUID version 4 string.
+std::string CreateRandomUuid();
+
 // Generates a random id.
 uint32_t CreateRandomId();