API add to set background noise mode.

Background noise mode.

BUG=
R=henrik.lundin@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2194005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@4835 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/audio_coding/neteq4/neteq_impl.h b/webrtc/modules/audio_coding/neteq4/neteq_impl.h
index 60e644f..c041680 100644
--- a/webrtc/modules/audio_coding/neteq4/neteq_impl.h
+++ b/webrtc/modules/audio_coding/neteq4/neteq_impl.h
@@ -173,15 +173,17 @@
 
   // Get sequence number and timestamp of the latest RTP.
   // This method is to facilitate NACK.
-  virtual int DecodedRtpInfo(int* sequence_number, uint32_t* timestamp);
+  virtual int DecodedRtpInfo(int* sequence_number, uint32_t* timestamp) const;
+
+  // Sets background noise mode.
+  virtual void SetBackgroundNoiseMode(NetEqBackgroundNoiseMode mode);
+
+  // Gets background noise mode.
+  virtual NetEqBackgroundNoiseMode BackgroundNoiseMode() const;
 
   virtual int InsertSyncPacket(const WebRtcRTPHeader& rtp_header,
                                  uint32_t receive_timestamp);
 
-  virtual void SetBackgroundNoiseMode(NetEqBackgroundNoiseMode mode);
-
-  virtual NetEqBackgroundNoiseMode BackgroundNoiseMode() const;
-
  private:
   static const int kOutputSizeMs = 10;
   static const int kMaxFrameSize = 2880;  // 60 ms @ 48 kHz.