visibility-decoration.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@114671 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/streambuf b/include/streambuf
index 2746d53..9515f3f 100644
--- a/include/streambuf
+++ b/include/streambuf
@@ -117,7 +117,7 @@
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _CharT, class _Traits>
-class basic_streambuf
+class _LIBCPP_VISIBLE basic_streambuf
 {
 public:
     // types: