PPAPI: Make blocking completion callbacks work.

ppapi/shared_impl/private/udp_socket_private_impl.h

Index: ppapi/shared_impl/private/udp_socket_private_impl.h
diff --git a/ppapi/shared_impl/private/udp_socket_private_impl.h b/ppapi/shared_impl/private/udp_socket_private_impl.h
index bb8a80ec3346aecec9f913cdf494a191ba22cf3c..36d51ca0e94b45ac4ea38ba305ba1e4f773451fe 100644
--- a/ppapi/shared_impl/private/udp_socket_private_impl.h
+++ b/ppapi/shared_impl/private/udp_socket_private_impl.h
@@ -41,16 +41,16 @@ class PPAPI_SHARED_EXPORT UDPSocketPrivateImpl
 
   // PPB_UDPSocket_Private_API implementation.
   virtual int32_t Bind(const PP_NetAddress_Private* addr,
-                       PP_CompletionCallback callback) OVERRIDE;
+                       scoped_refptr<TrackedCallback> callback) OVERRIDE;
   virtual PP_Bool GetBoundAddress(PP_NetAddress_Private* addr) OVERRIDE;
   virtual int32_t RecvFrom(char* buffer,
                            int32_t num_bytes,
-                           PP_CompletionCallback callback) OVERRIDE;
+                           scoped_refptr<TrackedCallback> callback) OVERRIDE;
   virtual PP_Bool GetRecvFromAddress(PP_NetAddress_Private* addr) OVERRIDE;
   virtual int32_t SendTo(const char* buffer,
                          int32_t num_bytes,
                          const PP_NetAddress_Private* addr,
-                         PP_CompletionCallback callback) OVERRIDE;
+                         scoped_refptr<TrackedCallback> callback) OVERRIDE;
   virtual void Close() OVERRIDE;
 
   // Notifications from the proxy.