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}

sdk/objc/native/src/audio/audio_device_ios.h

@@ -16,9 +16,9 @@
 #include "audio_session_observer.h"
 #include "modules/audio_device/audio_device_generic.h"
 #include "rtc_base/buffer.h"
+#include "rtc_base/synchronization/sequence_checker.h"
 #include "rtc_base/thread.h"
 #include "rtc_base/thread_annotations.h"
-#include "rtc_base/thread_checker.h"
 #include "sdk/objc/base/RTCMacros.h"
 #include "voice_processing_audio_unit.h"
 
@@ -210,10 +210,10 @@ class AudioDeviceIOS : public AudioDeviceGeneric,
 
   // Ensures that methods are called from the same thread as this object is
   // created on.
-  rtc::ThreadChecker thread_checker_;
+  SequenceChecker thread_checker_;
 
   // Native I/O audio thread checker.
-  rtc::ThreadChecker io_thread_checker_;
+  SequenceChecker io_thread_checker_;
 
   // Thread that this object is created on.
   rtc::Thread* thread_;