Discard frame self-dependency when parsing genric frame descriptor

Bug: chromium:859281
Change-Id: Ieb96f633a93f4f2e498bb1949339e239184bce9d
Reviewed-on: https://webrtc-review.googlesource.com/86545
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Alex Loiko <aleloi@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23817}

modules/rtp_rtcp/source/rtp_generic_frame_descriptor.cc

@@ -60,6 +60,8 @@ bool RtpGenericFrameDescriptor::AddFrameDependencyDiff(uint16_t fdiff) {
   RTC_DCHECK(FirstPacketInSubFrame());
   if (num_frame_deps_ == kMaxNumFrameDependencies)
     return false;
+  if (fdiff == 0)
+    return false;
   RTC_DCHECK_LT(fdiff, 1 << 14);
   RTC_DCHECK_GT(fdiff, 0);
   frame_deps_id_diffs_[num_frame_deps_] = fdiff;