Use SequenceChecker from public API

Bug: webrtc:12419
Change-Id: I00cca16a0ec70246156ba00b97aa7ae5ccbf5364
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/205323
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33220}
diff --git a/pc/peer_connection_message_handler.cc b/pc/peer_connection_message_handler.cc
index ea9df5a..4b7913d 100644
--- a/pc/peer_connection_message_handler.cc
+++ b/pc/peer_connection_message_handler.cc
@@ -16,11 +16,11 @@
 #include "api/media_stream_interface.h"
 #include "api/peer_connection_interface.h"
 #include "api/scoped_refptr.h"
+#include "api/sequence_checker.h"
 #include "api/stats_types.h"
 #include "pc/stats_collector_interface.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/location.h"
-#include "rtc_base/synchronization/sequence_checker.h"
 
 namespace webrtc {