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}

modules/utility/source/process_thread_impl.h

@@ -24,7 +24,7 @@
 #include "rtc_base/event.h"
 #include "rtc_base/location.h"
 #include "rtc_base/platform_thread.h"
-#include "rtc_base/thread_checker.h"
+#include "rtc_base/synchronization/sequence_checker.h"
 
 namespace webrtc {
 
@@ -95,7 +95,7 @@ class ProcessThreadImpl : public ProcessThread {
   rtc::RecursiveCriticalSection
       lock_;  // Used to guard modules_, tasks_ and stop_.
 
-  rtc::ThreadChecker thread_checker_;
+  SequenceChecker thread_checker_;
   rtc::Event wake_up_;
   // TODO(pbos): Remove unique_ptr and stop recreating the thread.
   std::unique_ptr<rtc::PlatformThread> thread_;