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

components/scheduler/renderer/renderer_scheduler_impl.cc

Index: components/scheduler/renderer/renderer_scheduler_impl.cc
diff --git a/components/scheduler/renderer/renderer_scheduler_impl.cc b/components/scheduler/renderer/renderer_scheduler_impl.cc
index 04d56f2dd523d141cae5b53f5ecb09063674ca0c..5e1740f45322b406706f4f944fb733ef2ccb66bb 100644
--- a/components/scheduler/renderer/renderer_scheduler_impl.cc
+++ b/components/scheduler/renderer/renderer_scheduler_impl.cc
@@ -29,6 +29,7 @@ const int kTimerTaskEstimationSampleCount = 1000;
 const double kTimerTaskEstimationPercentile = 99;
 const int kShortIdlePeriodDurationSampleCount = 10;
 const double kShortIdlePeriodDurationPercentile = 50;
+
 }
 
 RendererSchedulerImpl::RendererSchedulerImpl(
@@ -574,6 +575,11 @@ base::TimeTicks RendererSchedulerImpl::CurrentIdleTaskDeadlineForTesting()
   return idle_helper_.CurrentIdleTaskDeadline();
 }
 
+void RendererSchedulerImpl::RunIdleTasksForTesting(
+    const base::Closure& callback) {
+ idle_helper_.RunIdleTasksForTesting(callback);
+}
+
 void RendererSchedulerImpl::MaybeUpdatePolicy() {
   helper_.CheckOnValidThread();
   if (policy_may_need_update_.IsSet()) {