Replace rtc::ThreadChecker with webrtc::SequenceChecker

Bug: webrtc:12419
Change-Id: I825c014cc1c4b1dcba5ef300409d44859e971144
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/205002
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33136}
diff --git a/rtc_base/platform_thread.h b/rtc_base/platform_thread.h
index 4968de9..3438f8e 100644
--- a/rtc_base/platform_thread.h
+++ b/rtc_base/platform_thread.h
@@ -19,7 +19,7 @@
 #include "absl/strings/string_view.h"
 #include "rtc_base/constructor_magic.h"
 #include "rtc_base/platform_thread_types.h"
-#include "rtc_base/thread_checker.h"
+#include "rtc_base/synchronization/sequence_checker.h"
 
 namespace rtc {
 
@@ -84,8 +84,8 @@
   // TODO(pbos): Make sure call sites use string literals and update to a const
   // char* instead of a std::string.
   const std::string name_;
-  rtc::ThreadChecker thread_checker_;
-  rtc::ThreadChecker spawned_thread_checker_;
+  webrtc::SequenceChecker thread_checker_;
+  webrtc::SequenceChecker spawned_thread_checker_;
 #if defined(WEBRTC_WIN)
   static DWORD WINAPI StartThread(void* param);