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

ppapi/shared_impl/video_decoder_impl.cc

Index: ppapi/shared_impl/video_decoder_impl.cc
diff --git a/ppapi/shared_impl/video_decoder_impl.cc b/ppapi/shared_impl/video_decoder_impl.cc
index ae185c144887f4d67bf5fb9815fb662ee8971249..e665941c280bc0b5c1cb77dfd527731e1b9ee215 100644
--- a/ppapi/shared_impl/video_decoder_impl.cc
+++ b/ppapi/shared_impl/video_decoder_impl.cc
@@ -22,10 +22,6 @@ VideoDecoderImpl::VideoDecoderImpl()
       gles2_impl_(NULL) {
 }
 
-thunk::PPB_VideoDecoder_API* VideoDecoderImpl::AsPPB_VideoDecoder_API() {
-  return this;
-}
-
 VideoDecoderImpl::~VideoDecoderImpl() {
 }