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

ppapi/api/ppb_audio_frame.idl

Index: ppapi/api/ppb_audio_frame.idl
diff --git a/ppapi/api/ppb_audio_frame.idl b/ppapi/api/ppb_audio_frame.idl
index 660071690171dd9ed7e8e1c429ae73b862e18cf4..bb4d4b897fac2b813681d089de0888b38b0bf4b2 100644
--- a/ppapi/api/ppb_audio_frame.idl
+++ b/ppapi/api/ppb_audio_frame.idl
@@ -19,6 +19,7 @@ label Chrome {
  */
 enum PP_AudioFrame_SampleRate {
   PP_AUDIOFRAME_SAMPLERATE_UNKNOWN = 0,
+  PP_AUDIOFRAME_SAMPLERATE_8000 = 8000,
   PP_AUDIOFRAME_SAMPLERATE_44100 = 44100
 };
 
@@ -66,6 +67,17 @@ interface PPB_AudioFrame {
   void SetTimestamp([in] PP_Resource frame, [in] PP_TimeDelta timestamp);
 
   /**
+   * Gets the sample rate of the audio frame.
+   *
+   * @param[in] frame A <code>PP_Resource</code> corresponding to an audio frame
+   * resource.
+   *
+   * @return The sample rate of the audio frame.
+   */
+  [on_failure=PP_AUDIOFRAME_SAMPLERATE_UNKNOWN]
+  PP_AudioFrame_SampleRate GetSampleRate([in] PP_Resource frame);
+
+  /**
    * Gets the sample size of the audio frame.
    *
    * @param[in] frame A <code>PP_Resource</code> corresponding to an audio frame