[scheduler] Support setting maximal throttling duration

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 d18481751d9e14b06f8f24029969a79069aa57af..218ef775ce7b8e751f19e6943a2595a9eb09ddfe 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
@@ -69,7 +69,8 @@ class BLINK_PLATFORM_EXPORT TaskQueueThrottler : public TimeDomain::Observer {
     // is scheduled.
     void RemoveQueue(base::TimeTicks now, TaskQueue* queue);
 
-    void RecordTaskRunTime(base::TimeDelta task_run_time);
+    void RecordTaskRunTime(base::TimeTicks start_time,
+                           base::TimeTicks end_time);
 
     // Enables this time budget pool. Queues from this pool will be
     // throttled based on their run time.
@@ -95,7 +96,9 @@ class BLINK_PLATFORM_EXPORT TaskQueueThrottler : public TimeDomain::Observer {
 
     TimeBudgetPool(const char* name,
                    TaskQueueThrottler* task_queue_throttler,
-                   base::TimeTicks now);
+                   base::TimeTicks now,
+                   base::Optional<base::TimeDelta> max_budget_level,
+                   base::Optional<base::TimeDelta> max_throttling_duration);
 
     bool HasEnoughBudgetToRun(base::TimeTicks now);
     base::TimeTicks GetNextAllowedRunTime();
@@ -111,12 +114,22 @@ class BLINK_PLATFORM_EXPORT TaskQueueThrottler : public TimeDomain::Observer {
     // Disable all associated throttled queues.
     void BlockThrottledQueues(base::TimeTicks now);
 
+    // Increase current_budget_level_ to satisfy max throttling duration
+    // condition if necessary.
+    void EnforceMaximalThrottlingDuration();
+
     const char* name_;  // NOT OWNED
 
     TaskQueueThrottler* task_queue_throttler_;
 
+    // Max budget level is the maximal amount of time which the time budget pool
+    // is allowed to run for after a very long period of inactivity.

[Sami, 2016/10/14 00:33:02]

Hmm, is this the maximum budget we can accrue? This description is a little
confusing.

[altimin, 2016/10/14 16:18:55]

Rephrased.

+    base::Optional<base::TimeDelta> max_budget_level_;
+    // Max throttling duration is the amount of time after which the task will

[Sami, 2016/10/14 00:33:02]

Would it be simpler to say this is the maximum delay added to a task by
throttling? Is that accurate?

[altimin, 2016/10/14 16:18:55]

No. In fact, it's just a lower bound on time budget level (we're using
throttling duration instead of min budget level to make it throttling
aggressiveness-agnostic).

Rephrased.

+    // be run after a very long period of full activity.
+    base::Optional<base::TimeDelta> max_throttling_duration_;
+
     base::TimeDelta current_budget_level_;
-    base::TimeDelta max_budget_level_;
     base::TimeTicks last_checkpoint_;
     double cpu_percentage_;
     bool is_enabled_;
@@ -236,6 +249,9 @@ class BLINK_PLATFORM_EXPORT TaskQueueThrottler : public TimeDomain::Observer {
   const char* tracing_category_;               // NOT OWNED
   std::unique_ptr<ThrottledTimeDomain> time_domain_;
 
+  base::Optional<base::TimeDelta> max_budget_level_;
+  base::Optional<base::TimeDelta> max_throttling_duration_;
+
   CancelableClosureHolder pump_throttled_tasks_closure_;
   base::Optional<base::TimeTicks> pending_pump_throttled_tasks_runtime_;
   bool virtual_time_;