NetEq: Ask AudioDecoder for sample rate instead of passing it as an argument

BUG=webrtc:5801
NOTRY=true

Review-Url: https://codereview.webrtc.org/2027993002
Cr-Commit-Position: refs/heads/master@{#13162}
diff --git a/webrtc/modules/audio_coding/neteq/neteq_impl.h b/webrtc/modules/audio_coding/neteq/neteq_impl.h
index 2b10f97..e24dfb9 100644
--- a/webrtc/modules/audio_coding/neteq/neteq_impl.h
+++ b/webrtc/modules/audio_coding/neteq/neteq_impl.h
@@ -128,8 +128,7 @@
   int RegisterExternalDecoder(AudioDecoder* decoder,
                               NetEqDecoder codec,
                               const std::string& codec_name,
-                              uint8_t rtp_payload_type,
-                              int sample_rate_hz) override;
+                              uint8_t rtp_payload_type) override;
 
   // Removes |rtp_payload_type| from the codec database. Returns 0 on success,
   // -1 on failure.