Merge "Revert "unique_fd: easier to forward declare"" am: 9d599c3ec6 am: 9d64cee049 am: de0d84ec35

Original change: https://android-review.googlesource.com/c/platform/system/libbase/+/1690407

Change-Id: I87ff394dac9ccb07e56d9408c14f1a63a83fddc5

include/android-base/unique_fd.h

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