Use ffmpeg for opus decoding, no need to maintain our decoder.

media/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/buildflag_header.gni")
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/features.gni")
 import("//build/config/linux/pkg_config.gni")
 import("//build/config/ui.gni")
@@ skipping 144 matching lines @@
     "filters/h264_bit_reader.cc",
     "filters/h264_bit_reader.h",
     "filters/h264_parser.cc",
     "filters/h264_parser.h",
     "filters/ivf_parser.cc",
     "filters/ivf_parser.h",
     "filters/jpeg_parser.cc",
     "filters/jpeg_parser.h",
     "filters/memory_data_source.cc",
     "filters/memory_data_source.h",
-    "filters/opus_audio_decoder.cc",
-    "filters/opus_audio_decoder.h",
     "filters/opus_constants.cc",
     "filters/opus_constants.h",
     "filters/pipeline_controller.cc",
     "filters/pipeline_controller.h",
     "filters/source_buffer_range.cc",
     "filters/source_buffer_range.h",
     "filters/source_buffer_state.cc",
     "filters/source_buffer_state.h",
     "filters/source_buffer_stream.cc",
     "filters/source_buffer_stream.h",
@@ skipping 739 matching lines @@
   fuzzer_test("media_mp4_avcc_parser_fuzzer") {
     sources = [
       "formats/mp4/mp4_avcc_parser_fuzzer.cc",
     ]
     deps = [
       ":media",
       "//base",
     ]
   }
 }