Add missing header to fix build error when using linux system libraries

Change-Id: I4fc04563c2cfe36fa2352f72f2ae61d47972f025
Bug: webrtc:11226
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/268194
Owners-Override: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Alessio Bazzica <alessiob@webrtc.org>
Auto-Submit: Bruno Pitrus <brunopitrus@hotmail.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37555}
diff --git a/AUTHORS b/AUTHORS
index 1a000c1..5c88c7f 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -25,6 +25,7 @@
 Berthold Herrmann <bertholdherrmann08@googlemail.com>
 Bob Withers <bwit@pobox.com>
 Bridger Maxwell <bridgeyman@gmail.com>
+Bruno Pitrus <brunopitrus@hotmail.com>
 Cheng Qian <chengqian1521@qq.com>
 Christophe Dumez <ch.dumez@samsung.com>
 Chris Tserng <tserng@amazon.com>
diff --git a/modules/audio_processing/aec3/multi_channel_content_detector.h b/modules/audio_processing/aec3/multi_channel_content_detector.h
index 1c6cc1e..be8717f 100644
--- a/modules/audio_processing/aec3/multi_channel_content_detector.h
+++ b/modules/audio_processing/aec3/multi_channel_content_detector.h
@@ -13,6 +13,7 @@
 
 #include <stddef.h>
 
+#include <memory>
 #include <vector>
 
 #include "absl/types/optional.h"