Incorrect overhead calculation when using FEC + RTP extension headers.

When frames are fragmented inte multiple RTP packets in order to not
exceed a maximum packet size, the header overhead calculation must
take into account that FEC redundancy packets may use more than the
12 bytes of the basic RTP header. For example, a csrc list or extension
headers may be present.

BUG=2899
R=phoglund@webrtc.org, stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/8769005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5562 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/rtp_rtcp/source/fec_test_helper.h

@@ -16,9 +16,6 @@
 
 namespace webrtc {
 
-enum {
-  kRtpHeaderSize = 12
-};
 enum {
   kFecPayloadType = 96
 };