Deprecating ThreadChecker specific interface.

All changes outside thread_checker.h are by:
s/CalledOnValidThread/IsCurrent/
s/DetachFromThread/Detach/

Bug: webrtc:9883
Change-Id: Idbb1086bff0817db58e770116acf4c9d60fae8b3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/131023
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27494}
diff --git a/rtc_base/thread_checker.h b/rtc_base/thread_checker.h
index d3daa6f..876a08e 100644
--- a/rtc_base/thread_checker.h
+++ b/rtc_base/thread_checker.h
@@ -13,14 +13,15 @@
 #ifndef RTC_BASE_THREAD_CHECKER_H_
 #define RTC_BASE_THREAD_CHECKER_H_
 
+#include "rtc_base/deprecation.h"
 #include "rtc_base/synchronization/sequence_checker.h"
 
 namespace rtc {
 // TODO(srte): Replace usages of this with SequenceChecker.
 class ThreadChecker : public webrtc::SequenceChecker {
  public:
-  bool CalledOnValidThread() const { return IsCurrent(); }
-  void DetachFromThread() { Detach(); }
+  RTC_DEPRECATED bool CalledOnValidThread() const { return IsCurrent(); }
+  RTC_DEPRECATED void DetachFromThread() { Detach(); }
 };
 }  // namespace rtc
 #endif  // RTC_BASE_THREAD_CHECKER_H_