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

components/scheduler/child/idle_helper.cc

Index: components/scheduler/child/idle_helper.cc
diff --git a/components/scheduler/child/idle_helper.cc b/components/scheduler/child/idle_helper.cc
index e64be4fe22488464fdfcdf6b2781fafed24a38cb..927975db0109e3580e102c0e3dfb8287359968c9 100644
--- a/components/scheduler/child/idle_helper.cc
+++ b/components/scheduler/child/idle_helper.cc
@@ -197,6 +197,15 @@ void IdleHelper::EndIdlePeriod() {
                      base::TimeTicks());
 }
 
+void IdleHelper::RunIdleTasksForTesting(const base::Closure& callback) {
+  IdleTaskRunner()->PostIdleTask(
+      FROM_HERE,
+      base::Bind(&IdleHelper::EndIdlePeriodForTesting,
+                 weak_factory_.GetWeakPtr(),
+                 callback));
+  EnableLongIdlePeriod();
+}
+
 void IdleHelper::WillProcessTask(const base::PendingTask& pending_task) {
 }
 
@@ -256,6 +265,13 @@ void IdleHelper::UpdateLongIdlePeriodStateAfterIdleTask() {
   }
 }
 
+void IdleHelper::EndIdlePeriodForTesting(
+    const base::Closure& callback,
+    base::TimeTicks time_ticks) {
+  EndIdlePeriod();
+  callback.Run();
+}
+
 base::TimeTicks IdleHelper::CurrentIdleTaskDeadline() const {
   helper_->CheckOnValidThread();
   return state_.idle_period_deadline();