Remove ACMCodecDB::Codec, and make the rest of ACMCodecDB private

webrtc/modules/audio_coding/main/acm2/rent_a_codec.cc

 /*
  *  Copyright (c) 2015 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 11 matching lines @@
     int channels) {
   return CodecIdFromIndex(
       ACMCodecDB::CodecId(payload_name, sampling_freq_hz, channels));
 }
 
 rtc::Maybe<CodecInst> RentACodec::CodecInstById(CodecId codec_id) {
   rtc::Maybe<int> mi = CodecIndexFromId(codec_id);
   return mi ? rtc::Maybe<CodecInst>(Database()[*mi]) : rtc::Maybe<CodecInst>();
 }
 
+rtc::Maybe<RentACodec::CodecId> RentACodec::CodecIdByInst(
+    const CodecInst& codec_inst) {
+  return CodecIdFromIndex(ACMCodecDB::CodecNumber(codec_inst));
+}
+
 rtc::Maybe<CodecInst> RentACodec::CodecInstByParams(const char* payload_name,
                                                     int sampling_freq_hz,
                                                     int channels) {
   rtc::Maybe<CodecId> codec_id =
       CodecIdByParams(payload_name, sampling_freq_hz, channels);
   if (!codec_id)
     return rtc::Maybe<CodecInst>();
   rtc::Maybe<CodecInst> ci = CodecInstById(*codec_id);
   RTC_DCHECK(ci);
 
@@ skipping 28 matching lines @@
     return rtc::Maybe<NetEqDecoder>();
   const NetEqDecoder ned = ACMCodecDB::neteq_decoders_[*i];
   return rtc::Maybe<NetEqDecoder>(
       (ned == NetEqDecoder::kDecoderOpus && num_channels == 2)
           ? NetEqDecoder::kDecoderOpus_2ch
           : ned);
 }
 
 }  // namespace acm2
 }  // namespace webrtc