Make CodecType conversion functions non-optional.

webrtc/modules/video_coding/utility/ivf_file_writer.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 105 matching lines @@
   RTC_CHECK_GT(width_, 0);
   RTC_CHECK_GT(height_, 0);
   using_capture_timestamps_ = encoded_image._timeStamp == 0;
 
   codec_type_ = codec_type;
 
   if (!WriteHeader())
     return false;
 
   const char* codec_name =
-      CodecTypeToPayloadName(codec_type_).value_or("Unknown");
+      CodecTypeToPayloadString(codec_type_);
   LOG(LS_WARNING) << "Created IVF file for codec data of type " << codec_name
                   << " at resolution " << width_ << " x " << height_
                   << ", using " << (using_capture_timestamps_ ? "1" : "90")
                   << "kHz clock resolution.";
   return true;
 }
 
 bool IvfFileWriter::WriteFrame(const EncodedImage& encoded_image,
                                VideoCodecType codec_type) {
   if (!file_.IsOpen())
@@ skipping 54 matching lines @@
     file_.Close();
     return true;
   }
 
   bool ret = WriteHeader();
   file_.Close();
   return ret;
 }
 
 }  // namespace webrtc