AudioDecoder: New method SampleRateHz, + implementations for our codecs

webrtc/modules/audio_coding/codecs/isac/audio_decoder_isac_t.h

 /*
  *  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.
  */
 
 #ifndef WEBRTC_MODULES_AUDIO_CODING_CODECS_ISAC_AUDIO_DECODER_ISAC_T_H_
 #define WEBRTC_MODULES_AUDIO_CODING_CODECS_ISAC_AUDIO_DECODER_ISAC_T_H_
 
 #include <vector>
 
 #include "webrtc/base/constructormagic.h"
+#include "webrtc/base/optional.h"
 #include "webrtc/base/scoped_ref_ptr.h"
 #include "webrtc/modules/audio_coding/codecs/audio_decoder.h"
 #include "webrtc/modules/audio_coding/codecs/isac/locked_bandwidth_info.h"
 
 namespace webrtc {
 
+// TODO(kwiberg): Remove the possibility of not specifying the sample rate at
+// object creation time.
 template <typename T>
 class AudioDecoderIsacT final : public AudioDecoder {
  public:
   AudioDecoderIsacT();
   explicit AudioDecoderIsacT(
       const rtc::scoped_refptr<LockedIsacBandwidthInfo>& bwinfo);
+  explicit AudioDecoderIsacT(int sample_rate_hz);
+  AudioDecoderIsacT(int sample_rate_hz,
+                    const rtc::scoped_refptr<LockedIsacBandwidthInfo>& bwinfo);
   ~AudioDecoderIsacT() override;
 
   bool HasDecodePlc() const override;
   size_t DecodePlc(size_t num_frames, int16_t* decoded) override;
   void Reset() override;
   int IncomingPacket(const uint8_t* payload,
                      size_t payload_len,
                      uint16_t rtp_sequence_number,
                      uint32_t rtp_timestamp,
                      uint32_t arrival_timestamp) override;
   int ErrorCode() override;
+  int SampleRateHz() const override;
   size_t Channels() const override;
   int DecodeInternal(const uint8_t* encoded,
                      size_t encoded_len,
                      int sample_rate_hz,
                      int16_t* decoded,
                      SpeechType* speech_type) override;
 
  private:
+  AudioDecoderIsacT(rtc::Optional<int> sample_rate_hz,
+                    const rtc::scoped_refptr<LockedIsacBandwidthInfo>& bwinfo);
+
   typename T::instance_type* isac_state_;
+  rtc::Optional<int> sample_rate_hz_;
   rtc::scoped_refptr<LockedIsacBandwidthInfo> bwinfo_;
-  int decoder_sample_rate_hz_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(AudioDecoderIsacT);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_CODING_CODECS_ISAC_AUDIO_DECODER_ISAC_T_H_