[Cleanup] Migrate ExternalMetrics to use the Task Scheduler.

chromecast/browser/metrics/external_metrics.h

Index: chromecast/browser/metrics/external_metrics.h
diff --git a/chromecast/browser/metrics/external_metrics.h b/chromecast/browser/metrics/external_metrics.h
index 9e48da4902df63bf4d00798769f290ef1606d997..79cf6f7584b9b6abeaefd508ad1ee5d8ea24050c 100644
--- a/chromecast/browser/metrics/external_metrics.h
+++ b/chromecast/browser/metrics/external_metrics.h
@@ -10,6 +10,7 @@
 #include "base/callback_forward.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/sequence_checker.h"
 #include "base/sequenced_task_runner_helpers.h"
 
 namespace metrics {
@@ -62,12 +63,20 @@ class ExternalMetrics {
   // Calls CollectEvents and reschedules a future collection.
   void CollectEventsAndReschedule();
 
+  // Schedules a future collection.
+  void ScheduleCollection();
+
   // Reference to stability metrics provider, for reporting external crashes.
   CastStabilityMetricsProvider* const stability_provider_;
 
   // File used by libmetrics to send metrics to the browser process.
   const std::string uma_events_file_;
 
+  // The task runner used for running background tasks.
+  scoped_refptr<base::SequencedTaskRunner> task_runner_;
+
+  SEQUENCE_CHECKER(sequence_checker_);
+
   base::WeakPtrFactory<ExternalMetrics> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ExternalMetrics);