Add testRunner.runIdleTasks() to force idle tasks to run.

components/scheduler/child/idle_helper.h

Index: components/scheduler/child/idle_helper.h
diff --git a/components/scheduler/child/idle_helper.h b/components/scheduler/child/idle_helper.h
index 333c8674a36e85176d1420abda4543275d18c7ba..bea0e0ca56687a1a6243838bce05dd2e84d5aaf9 100644
--- a/components/scheduler/child/idle_helper.h
+++ b/components/scheduler/child/idle_helper.h
@@ -99,6 +99,11 @@ class SCHEDULER_EXPORT IdleHelper
   // EnableLongIdlePeriod.
   void EndIdlePeriod();
 
+  // Enter a long idle period that automatically ends when all queued
+  // idle tasks have run.  The callback argument will be run after the
+  // idle period ends.
+  void RunIdleTasksForTesting(const base::Closure& callback);
+
   // Returns true if a currently running idle task could exceed its deadline
   // without impacting user experience too much. This should only be used if
   // there is a task which cannot be pre-empted and is likely to take longer
@@ -187,6 +192,9 @@ class SCHEDULER_EXPORT IdleHelper
   void OnIdleTaskPostedOnMainThread();
   void UpdateLongIdlePeriodStateAfterIdleTask();
 
+  void EndIdlePeriodForTesting(const base::Closure& callback,
+                               base::TimeTicks time_remaining);
+
   void SetIdlePeriodState(IdlePeriodState new_state,
                           base::TimeTicks new_deadline,
                           base::TimeTicks optional_now);