[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..71b20b2870331dad0b096ae02f3a40007e87d0f1 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 +85,12 @@ 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. Throttling duration (time until the queue is allowed
+    // to run again) is passed as a parameter to callback.
+    void SetReportingCallback(
+        base::Callback<void(base::TimeDelta)> reporting_callback);
+
     // All queues should be removed before calling Close().
     void Close();
 
@@ -141,6 +147,8 @@ class BLINK_PLATFORM_EXPORT TaskQueueThrottler : public TimeDomain::Observer {
 
     std::unordered_set<TaskQueue*> associated_task_queues_;
 
+    base::Callback<void(base::TimeDelta)> reporting_callback_;
+
     DISALLOW_COPY_AND_ASSIGN(TimeBudgetPool);
   };