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..ab80704b3b4bf24c14376af8e6bb0ab985650cc4 100644
--- a/components/scheduler/child/idle_helper.h
+++ b/components/scheduler/child/idle_helper.h
@@ -124,6 +124,9 @@ class SCHEDULER_EXPORT IdleHelper
   IdlePeriodState SchedulerIdlePeriodState() const;
   static const char* IdlePeriodStateToString(IdlePeriodState state);
 
+  // Test helper
+  void RunIdleTasksForTesting(const base::Closure&);

[Sami, 2016/03/29 11:11:17]

In this implementation all the idle callbacks are basically getting given a 0 ms
time slice to do their work, right? I think we should make that an explicit
parameter here.

[szager1, 2016/04/06 08:43:17]

I changed the implementation to use a regular long idle period, so the tasks
will get a time slice based on the standard long idle period deadline.

+
  private:
   friend class BaseIdleHelperTest;
   friend class IdleHelperTest;