Also provide sample rate when registering decoders

This replaces the old practice of looking up the sample rate in a
table, which won't work when we add support for external decoders.

COAUTHOR=henrik.lundin@webrtc.org
BUG=4474
R=jmarusic@webrtc.org, minyue@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/54469004

Cr-Commit-Position: refs/heads/master@{#9276}
diff --git a/webrtc/modules/audio_coding/neteq/neteq_impl.h b/webrtc/modules/audio_coding/neteq/neteq_impl.h
index 76b23e3..248071f 100644
--- a/webrtc/modules/audio_coding/neteq/neteq_impl.h
+++ b/webrtc/modules/audio_coding/neteq/neteq_impl.h
@@ -117,11 +117,12 @@
 
   // Provides an externally created decoder object |decoder| to insert in the
   // decoder database. The decoder implements a decoder of type |codec| and
-  // associates it with |rtp_payload_type|. Returns kOK on success, kFail on
-  // failure.
+  // associates it with |rtp_payload_type|. The decoder will produce samples
+  // at the rate |sample_rate_hz|. Returns kOK on success, kFail on failure.
   int RegisterExternalDecoder(AudioDecoder* decoder,
                               enum NetEqDecoder codec,
-                              uint8_t rtp_payload_type) override;
+                              uint8_t rtp_payload_type,
+                              int sample_rate_hz) override;
 
   // Removes |rtp_payload_type| from the codec database. Returns 0 on success,
   // -1 on failure.