Introduce a FlatMap and FlatSet into WTF

third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h

Index: third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
diff --git a/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h b/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
index da66808172335e0d9c06d968a0482f191a08d6fc..26ca90f09344f50c6f321aebf6aecca9dcf77281 100644
--- a/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
+++ b/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
@@ -177,6 +177,14 @@ class BLINK_PLATFORM_EXPORT TaskQueueImpl final : public TaskQueue {
   // TimeDomain. Must be called from the main thread.
   void WakeUpForDelayedWork(LazyNow* lazy_now);
 
+  base::TimeTicks time_domain_wakeup() const {
+    return main_thread_only().time_domain_wakeup;
+  }
+
+  void set_time_domain_wakeup(base::TimeTicks time_domain_wakeup) {
+    main_thread_only().time_domain_wakeup = time_domain_wakeup;
+  }
+
  private:
   friend class WorkQueue;
   friend class WorkQueueTest;
@@ -218,6 +226,7 @@ class BLINK_PLATFORM_EXPORT TaskQueueImpl final : public TaskQueue {
     bool is_enabled;
     base::trace_event::BlameContext* blame_context;  // Not owned.
     EnqueueOrder current_fence;
+    base::TimeTicks time_domain_wakeup;
   };
 
   ~TaskQueueImpl() override;