[scheduler] CPUTimeBudgetPool: Require a minimal level of budget to run

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

Index: third_party/WebKit/Source/platform/scheduler/renderer/budget_pool.h
diff --git a/third_party/WebKit/Source/platform/scheduler/renderer/budget_pool.h b/third_party/WebKit/Source/platform/scheduler/renderer/budget_pool.h
index 1ece45aadd661b4aaa99392912c01368afbcc3e6..187daccff5cca142c44519d22b2edfcc9811e6b4 100644
--- a/third_party/WebKit/Source/platform/scheduler/renderer/budget_pool.h
+++ b/third_party/WebKit/Source/platform/scheduler/renderer/budget_pool.h
@@ -84,12 +84,38 @@ class BLINK_PLATFORM_EXPORT CPUTimeBudgetPool : public BudgetPool {
  public:
   CPUTimeBudgetPool(const char* name,
                     BudgetPoolController* budget_pool_controller,
-                    base::TimeTicks now,
-                    base::Optional<base::TimeDelta> max_budget_level,
-                    base::Optional<base::TimeDelta> max_throttling_duration);
+                    base::TimeTicks now);
 
   ~CPUTimeBudgetPool();
 
+  // Set max budget level, base::nullopt represent absence of max level.
+  // Max budget level prevents accumulating arbitrary large budgets when
+  // page is inactive for a very long time.
+  void SetMaxBudgetLevel(base::TimeTicks now,
+                         base::Optional<base::TimeDelta> max_budget_level);
+
+  // Set max throttling duration, base::nullopt represents absense of it.
+  // Max throttling duration prevents page from being throttled for
+  // a very long period after a single long task.
+  void SetMaxThrottlingDelay(
+      base::TimeTicks now,
+      base::Optional<base::TimeDelta> max_throttling_delay);
+
+  // Set minimal budget level required to run a task. If budget pool was
+  // exhausted, it needs to accumulate at least |min_budget_to_run| time units
+  // to unblock and run tasks again. When unblocked, it still can run tasks
+  // when budget is positive but less than this level until being blocked
+  // until being blocked when budget reaches zero.
+  // This is needed for integration with WakeupBudgetPool to prevent a situation
+  // when wakeup happened but time budget pool allows only one task to run at
+  // the moment.
+  // It is recommended to use the same value for this and WakeupBudgetPool's
+  // wakeup window length.
+  // NOTE: This does not have an immediate effect and does not call
+  // BudgetPoolController::UnblockQueue.
+  void SetMinBudgetLevelToRun(base::TimeTicks now,
+                              base::TimeDelta min_budget_level_to_run);
+
   // Throttle task queues from this time budget pool if tasks are running
   // for more than |cpu_percentage| per cent of wall time.
   // This function does not affect internal time budget level.
@@ -142,12 +168,14 @@ class BLINK_PLATFORM_EXPORT CPUTimeBudgetPool : public BudgetPool {
   // Tasks will be allowed to run for this time before being throttled
   // after a very long period of inactivity.
   base::Optional<base::TimeDelta> max_budget_level_;
-  // Max throttling duration places a lower limit on time budget level,
+  // Max throttling delay places a lower limit on time budget level,
   // ensuring that one long task does not cause extremely long throttling.
-  // Note that this is not the guarantee that every task will run
+  // Note that this is not a guarantee that every task will run
   // after desired run time + max throttling duration, but a guarantee
-  // that at least one task will be run every max_throttling_duration.
-  base::Optional<base::TimeDelta> max_throttling_duration_;
+  // that at least one task will be run every max_throttling_delay.
+  base::Optional<base::TimeDelta> max_throttling_delay_;
+  // See CPUTimeBudgetPool::SetMinBudgetLevelToRun.
+  base::TimeDelta min_budget_level_to_run_;
 
   base::TimeDelta current_budget_level_;
   base::TimeTicks last_checkpoint_;