[Battery]: Delay start of CallStats.

To avoid unnecessary repeating tasks, CallStats' timer is started only
upon Call::EnsureStarted().

Bug: chromium:1152887
Change-Id: I1015315f42127bf510affc3d22c930b20eac8bba
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/206880
Commit-Queue: Tommi <tommi@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33232}

call/call.cc

@@ -686,6 +686,8 @@ void Call::EnsureStarted() {
   }
   is_started_ = true;
 
+  call_stats_->EnsureStarted();
+
   // This call seems to kick off a number of things, so probably better left
   // off being kicked off on request rather than in the ctor.
   transport_send_ptr_->RegisterTargetTransferRateObserver(this);

video/call_stats2.cc

@@ -77,11 +77,6 @@ CallStats::CallStats(Clock* clock, TaskQueueBase* task_queue)
       task_queue_(task_queue) {
   RTC_DCHECK(task_queue_);
   RTC_DCHECK_RUN_ON(task_queue_);
-  repeating_task_ =
-      RepeatingTaskHandle::DelayedStart(task_queue_, kUpdateInterval, [this]() {
-        UpdateAndReport();
-        return kUpdateInterval;
-      });
 }
 
 CallStats::~CallStats() {
@@ -93,6 +88,15 @@ CallStats::~CallStats() {
   UpdateHistograms();
 }
 
+void CallStats::EnsureStarted() {
+  RTC_DCHECK_RUN_ON(task_queue_);
+  repeating_task_ =
+      RepeatingTaskHandle::DelayedStart(task_queue_, kUpdateInterval, [this]() {
+        UpdateAndReport();
+        return kUpdateInterval;
+      });
+}
+
 void CallStats::UpdateAndReport() {
   RTC_DCHECK_RUN_ON(task_queue_);
 

video/call_stats2.h

@@ -35,6 +35,9 @@ class CallStats {
   CallStats(Clock* clock, TaskQueueBase* task_queue);
   ~CallStats();
 
+  // Ensure that necessary repeating tasks are started.
+  void EnsureStarted();
+
   // Expose an RtcpRttStats implementation without inheriting from RtcpRttStats.
   // That allows us to separate the threading model of how RtcpRttStats is
   // used (mostly on a process thread) and how CallStats is used (mostly on

video/call_stats2_unittest.cc

@@ -38,7 +38,10 @@ class MockStatsObserver : public CallStatsObserver {
 
 class CallStats2Test : public ::testing::Test {
  public:
-  CallStats2Test() { process_thread_->Start(); }
+  CallStats2Test() {
+    call_stats_.EnsureStarted();
+    process_thread_->Start();
+  }
 
   ~CallStats2Test() override { process_thread_->Stop(); }