[scheduler] Report background timer throttling intervention.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_THROTTLING_HELPER_H_
 #define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_THROTTLING_HELPER_H_
 
 #include <set>
 #include <unordered_map>
 
@@ skipping 67 matching lines @@
     // Disables with time budget pool. Queues from this pool will not be
     // throttled based on their run time. A call to |PumpThrottledTasks|
     // will be scheduled to enable this queues back again and respect
     // timer alignment. Internal budget level will not regenerate with time.
     void DisableThrottling(LazyNow* now);
 
     bool IsThrottlingEnabled() const;
 
     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();
 
    private:
     friend class TaskQueueThrottler;
 
     FRIEND_TEST_ALL_PREFIXES(TaskQueueThrottlerTest, TimeBudgetPool);
 
     TimeBudgetPool(const char* name,
                    TaskQueueThrottler* task_queue_throttler,
@@ skipping 36 matching lines @@
     // that at least one task will be run every max_throttling_duration.
     base::Optional<base::TimeDelta> max_throttling_duration_;
 
     base::TimeDelta current_budget_level_;
     base::TimeTicks last_checkpoint_;
     double cpu_percentage_;
     bool is_enabled_;
 
     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);
   };
 
   // TODO(altimin): Do not pass tracing category as const char*,
   // hard-code string instead.
   TaskQueueThrottler(RendererSchedulerImpl* renderer_scheduler,
                      const char* tracing_category);
 
   ~TaskQueueThrottler() override;
 
@@ skipping 116 matching lines @@
 
   base::WeakPtrFactory<TaskQueueThrottler> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TaskQueueThrottler);
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_THROTTLING_HELPER_H_