init: Add diagnostics for signalfd epoll failures.

Bug: 222441619
Test: inject failure with close, check for log messages
Change-Id: Ia18b88841779e230d00a6c47aaed4952b1444f85
diff --git a/init/epoll.h b/init/epoll.h
index 0df5289..f58ae8d 100644
--- a/init/epoll.h
+++ b/init/epoll.h
@@ -46,8 +46,13 @@
             std::optional<std::chrono::milliseconds> timeout);
 
   private:
+    struct Info {
+        std::shared_ptr<Handler> handler;
+        uint32_t events;
+    };
+
     android::base::unique_fd epoll_fd_;
-    std::map<int, std::shared_ptr<Handler>> epoll_handlers_;
+    std::map<int, Info> epoll_handlers_;
 };
 
 }  // namespace init