Separate the create and start phases in SchedulerWorkerPoolImpl.

base/task_scheduler/priority_queue.h

 // Copyright 2016 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 BASE_TASK_SCHEDULER_PRIORITY_QUEUE_H_
 #define BASE_TASK_SCHEDULER_PRIORITY_QUEUE_H_
 
 #include <memory>
 #include <queue>
 #include <vector>
@@ skipping 37 matching lines @@
     // Cannot be called on an empty PriorityQueue.
     const SequenceSortKey& PeekSortKey() const;
 
     // Removes and returns the highest priority Sequence in this PriorityQueue.
     // Cannot be called on an empty PriorityQueue.
     scoped_refptr<Sequence> PopSequence();
 
     // Returns true if the PriorityQueue is empty.
     bool IsEmpty() const;
 
+    // Returns the number of Sequences in the PriorityQueue.
+    size_t Size() const;
+
    private:
     friend class PriorityQueue;
 
     explicit Transaction(PriorityQueue* outer_queue);
 
     // Holds the lock of |outer_queue_| for the lifetime of this Transaction.
     AutoSchedulerLock auto_lock_;
 
     PriorityQueue* const outer_queue_;
 
@@ skipping 24 matching lines @@
 
   ContainerType container_;
 
   DISALLOW_COPY_AND_ASSIGN(PriorityQueue);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_PRIORITY_QUEUE_H_