[Battery]: TaskQueuePacedSender not started by default.

Following up on https://webrtc-review.googlesource.com/c/src/+/213000
This CL prevents scheduling work before TaskQueuePacedSender::EnsureStarted(),
making it necessary to function.

Bug: chromium:1152887
Change-Id: I848c9e6d6057a404626ad693b1f4dc7fba797a9c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/214320
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#33695}
diff --git a/modules/pacing/task_queue_paced_sender.h b/modules/pacing/task_queue_paced_sender.h
index e04fc19..0673441 100644
--- a/modules/pacing/task_queue_paced_sender.h
+++ b/modules/pacing/task_queue_paced_sender.h
@@ -154,9 +154,7 @@
 
   // Indicates if this task queue is started. If not, don't allow
   // posting delayed tasks yet.
-  // TODO(crbug.com/1152887): Initialize to false once all users call
-  // EnsureStarted().
-  bool is_started_ RTC_GUARDED_BY(task_queue_) = true;
+  bool is_started_ RTC_GUARDED_BY(task_queue_) = false;
 
   // Indicates if this task queue is shutting down. If so, don't allow
   // posting any more delayed tasks as that can cause the task queue to
diff --git a/modules/pacing/task_queue_paced_sender_unittest.cc b/modules/pacing/task_queue_paced_sender_unittest.cc
index ce26651..3806ec2 100644
--- a/modules/pacing/task_queue_paced_sender_unittest.cc
+++ b/modules/pacing/task_queue_paced_sender_unittest.cc
@@ -562,8 +562,7 @@
               kProbingRate * TimeDelta::Millis(1) + DataSize::Bytes(1));
   }
 
-  // TODO(crbug.com/1152887): Enable once pacer no longer auto-starts.
-  TEST(TaskQueuePacedSenderTest, DISABLED_NoStatsUpdatesBeforeStart) {
+  TEST(TaskQueuePacedSenderTest, NoStatsUpdatesBeforeStart) {
     const TimeDelta kCoalescingWindow = TimeDelta::Millis(5);
     GlobalSimulatedTimeController time_controller(Timestamp::Millis(1234));
     MockPacketRouter packet_router;