Add an idle task to periodically sweep canceled delayed tasks

third_party/WebKit/Source/platform/scheduler/child/idle_helper.h

Index: third_party/WebKit/Source/platform/scheduler/child/idle_helper.h
diff --git a/third_party/WebKit/Source/platform/scheduler/child/idle_helper.h b/third_party/WebKit/Source/platform/scheduler/child/idle_helper.h
index 5f0ccd7a182598f7c092feb79723a7680045d453..602f1b2e09b8dcb3ed8c981ee8eb85d2ccf462b5 100644
--- a/third_party/WebKit/Source/platform/scheduler/child/idle_helper.h
+++ b/third_party/WebKit/Source/platform/scheduler/child/idle_helper.h
@@ -138,6 +138,7 @@ class BLINK_PLATFORM_EXPORT IdleHelper
   void OnIdleTaskPosted() override;
   base::TimeTicks WillProcessIdleTask() override;
   void DidProcessIdleTask() override;
+  base::TimeTicks NowTicks() override;
 
   // base::MessageLoop::TaskObserver implementation:
   void WillProcessTask(const base::PendingTask& pending_task) override;
@@ -150,6 +151,8 @@ class BLINK_PLATFORM_EXPORT IdleHelper
   friend class BaseIdleHelperTest;
   friend class IdleHelperTest;
 
+  const scoped_refptr<TaskQueue>& idle_queue() const { return idle_queue_; }
+
   class State {
    public:
     State(SchedulerHelper* helper,