[PPAPI] Pepper MediaStream API audio track implementation and example.

ppapi/cpp/audio_frame.h

Index: ppapi/cpp/audio_frame.h
diff --git a/ppapi/cpp/audio_frame.h b/ppapi/cpp/audio_frame.h
index 32d55956e67616d0f627799392e98f63f5e15c10..1334a1388b00a7a10f451054c5ea069f4b4266d7 100644
--- a/ppapi/cpp/audio_frame.h
+++ b/ppapi/cpp/audio_frame.h
@@ -47,6 +47,11 @@ class AudioFrame : public Resource {
   /// audio stream.
   void SetTimestamp(PP_TimeDelta timestamp);
 
+  /// Gets the sample rate of the audio frame.
+  ///
+  /// @return The sample rate of the audio frame.
+  PP_AudioSampleRate GetSampleRate() const;
+
   /// Gets the sample size of the audio frame in bytes.
   ///
   /// @return The sample size of the audio frame in bytes.