Move the refcounting from the proxy/impl resource object to the shared resource object base class.

ppapi/shared_impl/audio_impl.cc

Index: ppapi/shared_impl/audio_impl.cc
diff --git a/ppapi/shared_impl/audio_impl.cc b/ppapi/shared_impl/audio_impl.cc
index 42254f5ed151ceb2e959533e8cd43a8cd123d0d3..b684ab1263c460c0b89c9d9de81c83b9d161b17f 100644
--- a/ppapi/shared_impl/audio_impl.cc
+++ b/ppapi/shared_impl/audio_impl.cc
@@ -25,10 +25,6 @@ AudioImpl::~AudioImpl() {
   }
 }
 
-::ppapi::thunk::PPB_Audio_API* AudioImpl::AsPPB_Audio_API() {
-  return this;
-}
-
 void AudioImpl::SetCallback(PPB_Audio_Callback callback, void* user_data) {
   callback_ = callback;
   user_data_ = user_data;