Merge "unique_fd: easier to forward declare" am: ee8f03853c am: b1ae44f9e5 am: a98bc8a6f9

Original change: https://android-review.googlesource.com/c/platform/system/libbase/+/1686819

Change-Id: Ieb5b97bb21855a841b257030ab55ca0785ab1931

include/android-base/unique_fd.h

diff --git a/include/android-base/unique_fd.h b/include/android-base/unique_fd.h
index 9ceb5db..6d89c07 100644
--- a/include/android-base/unique_fd.h
+++ b/include/android-base/unique_fd.h
@@ -85,7 +85,7 @@
 };
 
 template <typename Closer>
-class unique_fd_impl final {
+class unique_fd_impl {
  public:
   unique_fd_impl() {}
 
@@ -175,7 +175,9 @@
   }
 };
 
-using unique_fd = unique_fd_impl<DefaultCloser>;
+class unique_fd final : public unique_fd_impl<DefaultCloser> {
+  using unique_fd_impl::unique_fd_impl;
+};
 
 #if !defined(_WIN32)