[scheduler] Report background timer throttling intervention.

third_party/WebKit/Source/platform/scheduler/renderer/task_queue_throttler.h

Index: third_party/WebKit/Source/platform/scheduler/renderer/task_queue_throttler.h
diff --git a/third_party/WebKit/Source/platform/scheduler/renderer/task_queue_throttler.h b/third_party/WebKit/Source/platform/scheduler/renderer/task_queue_throttler.h
index 9829a6814ddcc48893c6dcc8c467824fcd31623a..c74dbf341f47c45ae13adb43ab886326378bd06b 100644
--- a/third_party/WebKit/Source/platform/scheduler/renderer/task_queue_throttler.h
+++ b/third_party/WebKit/Source/platform/scheduler/renderer/task_queue_throttler.h
@@ -85,6 +85,11 @@ class BLINK_PLATFORM_EXPORT TaskQueueThrottler : public TimeDomain::Observer {
 
     const char* Name() const;
 
+    // Set callback which will be called every time when this budget pool
+    // is throttled.

[Sami, 2016/11/04 17:51:49]

Please explain what value the callback is given too.

[alex clarke (OOO till 29th), 2016/11/07 16:53:10]

+1 You could consider naming it here.

[altimin, 2016/11/07 17:25:30]

Done.

+    void SetReportingCallback(
+        base::Callback<void(base::TimeDelta)> reporting_callback);
+
     // All queues should be removed before calling Close().
     void Close();
 
@@ -141,6 +146,8 @@ class BLINK_PLATFORM_EXPORT TaskQueueThrottler : public TimeDomain::Observer {
 
     std::unordered_set<TaskQueue*> associated_task_queues_;
 
+    base::Optional<base::Callback<void(base::TimeDelta)>> reporting_callback_;

[alex clarke (OOO till 29th), 2016/11/07 16:53:10]

Do we really need base::Optional? base::Callback has a default constructor that
does nothing for which is_null returns true.

+
     DISALLOW_COPY_AND_ASSIGN(TimeBudgetPool);
   };