Deprecate RTPFragmentationHeader argument to VideoDecoder::Decode

Intend to delete in a later cl.

Bug: webrtc:6471
Change-Id: Icf0fcd40e0d3287dc59b684fae6552b40b47204a
Reviewed-on: https://webrtc-review.googlesource.com/39511
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23162}

modules/video_coding/codecs/h264/h264_decoder_impl.h

@@ -49,7 +49,6 @@ class H264DecoderImpl : public H264Decoder {
   // |missing_frames|, |fragmentation| and |render_time_ms| are ignored.
   int32_t Decode(const EncodedImage& input_image,
                  bool /*missing_frames*/,
-                 const RTPFragmentationHeader* /*fragmentation*/,
                  const CodecSpecificInfo* codec_specific_info = nullptr,
                  int64_t render_time_ms = -1) override;