Revert back to using the task_queue_ for guarding access.

This removes the SequenceChecker that was temporarily used while
the rtc::Thread TQ implementation was being fixed.

Bug: none
Change-Id: Iaa46e47371211ac0a97b2dcaf23cef12b43ee8ea
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/175081
Commit-Queue: Tommi <tommi@webrtc.org>
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31256}
diff --git a/rtc_base/task_utils/repeating_task.cc b/rtc_base/task_utils/repeating_task.cc
index 71911e6..3b84701 100644
--- a/rtc_base/task_utils/repeating_task.cc
+++ b/rtc_base/task_utils/repeating_task.cc
@@ -21,13 +21,12 @@
                                      TimeDelta first_delay)
     : task_queue_(task_queue),
       next_run_time_(Timestamp::Micros(rtc::TimeMicros()) + first_delay) {
-  sequence_checker_.Detach();
 }
 
 RepeatingTaskBase::~RepeatingTaskBase() = default;
 
 bool RepeatingTaskBase::Run() {
-  RTC_DCHECK_RUN_ON(&sequence_checker_);
+  RTC_DCHECK_RUN_ON(task_queue_);
   // Return true to tell the TaskQueue to destruct this object.
   if (next_run_time_.IsPlusInfinity())
     return true;
@@ -53,7 +52,7 @@
 }
 
 void RepeatingTaskBase::Stop() {
-  RTC_DCHECK_RUN_ON(&sequence_checker_);
+  RTC_DCHECK_RUN_ON(task_queue_);
   RTC_DCHECK(next_run_time_.IsFinite());
   next_run_time_ = Timestamp::PlusInfinity();
 }