Move AudioDecoderIsac* to its own files

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

Index: webrtc/modules/audio_coding/codecs/isac/audio_encoder_isac_t.h
diff --git a/webrtc/modules/audio_coding/codecs/isac/audio_encoder_isac_t.h b/webrtc/modules/audio_coding/codecs/isac/audio_encoder_isac_t.h
index 50d369ba35f397253201027ce39b374ee35c3a8c..6b361b4146eb98bcf90dd47c3936e822c467c3c3 100644
--- a/webrtc/modules/audio_coding/codecs/isac/audio_encoder_isac_t.h
+++ b/webrtc/modules/audio_coding/codecs/isac/audio_encoder_isac_t.h
@@ -13,7 +13,6 @@
 
 #include <vector>
 
-#include "webrtc/modules/audio_coding/codecs/audio_decoder.h"
 #include "webrtc/modules/audio_coding/codecs/audio_encoder.h"
 #include "webrtc/modules/audio_coding/codecs/isac/locked_bandwidth_info.h"
 
@@ -94,36 +93,5 @@ class AudioEncoderIsacT final : public AudioEncoder {
   RTC_DISALLOW_COPY_AND_ASSIGN(AudioEncoderIsacT);
 };
 
-template <typename T>
-class AudioDecoderIsacT final : public AudioDecoder {
- public:
-  AudioDecoderIsacT();
-  explicit AudioDecoderIsacT(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;
-  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:
-  typename T::instance_type* isac_state_;
-  LockedIsacBandwidthInfo* bwinfo_;
-  int decoder_sample_rate_hz_;
-
-  RTC_DISALLOW_COPY_AND_ASSIGN(AudioDecoderIsacT);
-};
-
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_AUDIO_CODING_CODECS_ISAC_AUDIO_ENCODER_ISAC_T_H_