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

ppapi/cpp/audio_frame.cc

Index: ppapi/cpp/audio_frame.cc
diff --git a/ppapi/cpp/audio_frame.cc b/ppapi/cpp/audio_frame.cc
index 7c3a1bbf894857e2f2d0ad93a0b7a099e6986976..538b689729edbc3a72a71c0f922c9c5366317cd3 100644
--- a/ppapi/cpp/audio_frame.cc
+++ b/ppapi/cpp/audio_frame.cc
@@ -44,6 +44,12 @@ void AudioFrame::SetTimestamp(PP_TimeDelta timestamp) {
     get_interface<PPB_AudioFrame_0_1>()->SetTimestamp(pp_resource(), timestamp);
 }
 
+PP_AudioSampleRate AudioFrame::GetSampleRate() const {
+  if (has_interface<PPB_AudioFrame_0_1>())
+    return get_interface<PPB_AudioFrame_0_1>()->GetSampleRate(pp_resource());
+  return PP_AUDIOSAMPLERATE_NONE;
+}
+
 uint32_t AudioFrame::GetSampleSize() const {
   if (has_interface<PPB_AudioFrame_0_1>())
     return get_interface<PPB_AudioFrame_0_1>()->GetSampleSize(pp_resource());