add missing includes for the build with use_libcxx_modules

This is to fix build error when we set use_libcxx_modules=true in
chromium build.

Bug: chromium:40440396
Change-Id: I5ab1cfcc0d060021892aae0e5ff3f0b647ae4266
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/370860
Commit-Queue: Takuto Ikuta <tikuta@google.com>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Auto-Submit: Takuto Ikuta <tikuta@google.com>
Cr-Commit-Position: refs/heads/main@{#43541}

modules/audio_coding/neteq/reorder_optimizer.cc

@@ -10,6 +10,8 @@
 
 #include "modules/audio_coding/neteq/reorder_optimizer.h"
 
+#include <stdint.h>
+
 #include <algorithm>
 #include <limits>
 #include <vector>

modules/audio_processing/aec3/multi_channel_content_detector.h

@@ -12,6 +12,7 @@
 #define MODULES_AUDIO_PROCESSING_AEC3_MULTI_CHANNEL_CONTENT_DETECTOR_H_
 
 #include <stddef.h>
+#include <stdint.h>
 
 #include <memory>
 #include <optional>

modules/portal/xdg_session_details.h

@@ -12,6 +12,7 @@
 #define MODULES_PORTAL_XDG_SESSION_DETAILS_H_
 
 #include <gio/gio.h>
+#include <stdint.h>
 
 #include <string>
 

video/stats_counter.h

@@ -11,6 +11,8 @@
 #ifndef VIDEO_STATS_COUNTER_H_
 #define VIDEO_STATS_COUNTER_H_
 
+#include <stdint.h>
+
 #include <memory>
 #include <string>