Handle delayed tasks more natively in the scheduler

cc/test/ordered_simple_task_runner.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_TEST_ORDERED_SIMPLE_TASK_RUNNER_H_
 #define CC_TEST_ORDERED_SIMPLE_TASK_RUNNER_H_
 
 #include <limits>
 #include <set>
 #include <vector>
@@ skipping 55 matching lines @@
   // prevent infinite task loops.
   static const size_t kAbsoluteMaxTasks;
   void SetRunTaskLimit(size_t max_tasks) { max_tasks_ = max_tasks; }
   void ClearRunTaskLimit() { max_tasks_ = kAbsoluteMaxTasks; }
 
   // Allow task runner to advance now when running tasks.
   void SetAutoAdvanceNowToPendingTasks(bool advance_now) {
     advance_now_ = advance_now;
   }
 
+  size_t NumPendingTasks() const;
   bool HasPendingTasks() const;
   base::TimeTicks NextTaskTime();
   base::TimeDelta DelayToNextTaskTime();
 
   // Run tasks while the callback returns true or too many tasks have been run.
   // Returns true if there are still pending tasks left.
   bool RunTasksWhile(base::Callback<bool(void)> condition);
 
   // Run tasks while *all* of the callbacks return true or too many tasks have
   // been run. Exits on the *first* condition which returns false, skipping
@@ skipping 58 matching lines @@
   bool inside_run_tasks_until_;
   std::set<TestOrderablePendingTask> pending_tasks_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OrderedSimpleTaskRunner);
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_ORDERED_SIMPLE_TASK_RUNNER_H_