AudioDecoder: New method SampleRateHz, + implementations for our codecs

webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.cc

Index: webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.cc
diff --git a/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.cc b/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.cc
index 9757b4a0100674095353e9e20e43f986a1b3aba8..af164c4bb72b0b25525b3999f3e6887390a0b802 100644
--- a/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.cc
+++ b/webrtc/modules/audio_coding/codecs/g711/audio_decoder_pcm.cc
@@ -16,6 +16,10 @@ namespace webrtc {
 
 void AudioDecoderPcmU::Reset() {}
 
+int AudioDecoderPcmU::SampleRateHz() const {
+  return 8000;
+}
+
 size_t AudioDecoderPcmU::Channels() const {
   return num_channels_;
 }
@@ -25,7 +29,7 @@ int AudioDecoderPcmU::DecodeInternal(const uint8_t* encoded,
                                      int sample_rate_hz,
                                      int16_t* decoded,
                                      SpeechType* speech_type) {
-  RTC_DCHECK_EQ(sample_rate_hz, 8000);
+  RTC_DCHECK_EQ(SampleRateHz(), sample_rate_hz);
   int16_t temp_type = 1;  // Default is speech.
   size_t ret = WebRtcG711_DecodeU(encoded, encoded_len, decoded, &temp_type);
   *speech_type = ConvertSpeechType(temp_type);
@@ -40,6 +44,10 @@ int AudioDecoderPcmU::PacketDuration(const uint8_t* encoded,
 
 void AudioDecoderPcmA::Reset() {}
 
+int AudioDecoderPcmA::SampleRateHz() const {
+  return 8000;
+}
+
 size_t AudioDecoderPcmA::Channels() const {
   return num_channels_;
 }
@@ -49,7 +57,7 @@ int AudioDecoderPcmA::DecodeInternal(const uint8_t* encoded,
                                      int sample_rate_hz,
                                      int16_t* decoded,
                                      SpeechType* speech_type) {
-  RTC_DCHECK_EQ(sample_rate_hz, 8000);
+  RTC_DCHECK_EQ(SampleRateHz(), sample_rate_hz);
   int16_t temp_type = 1;  // Default is speech.
   size_t ret = WebRtcG711_DecodeA(encoded, encoded_len, decoded, &temp_type);
   *speech_type = ConvertSpeechType(temp_type);