Adding a payload type to AudioEncoder objects

The type is set in the Config struct and is provided in the EncodedInfo
output struct from each Encode() call. The audio_decoder_unittest is
updated to verify correct propagation of the payload type.

BUG=3926
R=kwiberg@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/27299004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7780 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/audio_coding/codecs/opus/interface/audio_encoder_opus.h

@@ -25,6 +25,7 @@ class AudioEncoderOpus : public AudioEncoder {
     bool IsOk() const;
     int frame_size_ms;
     int num_channels;
+    int payload_type;
   };
 
   explicit AudioEncoderOpus(const Config& config);
@@ -45,6 +46,7 @@ class AudioEncoderOpus : public AudioEncoder {
  private:
   const int num_10ms_frames_per_packet_;
   const int num_channels_;
+  const int payload_type_;
   const int samples_per_10ms_frame_;
   std::vector<int16_t> input_buffer_;
   OpusEncInst* inst_;