Separate the create and start phases in SchedulerWorkerPoolImpl.

base/task_scheduler/priority_queue.cc

 // 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.
 
 #include "base/task_scheduler/priority_queue.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 75 matching lines @@
           outer_queue_->container_.top())
           .take_sequence();
   outer_queue_->container_.pop();
   return sequence;
 }
 
 bool PriorityQueue::Transaction::IsEmpty() const {
   return outer_queue_->container_.empty();
 }
 
+size_t PriorityQueue::Transaction::Size() const {
+  return outer_queue_->container_.size();
+}
+
 PriorityQueue::PriorityQueue() = default;
 
 PriorityQueue::~PriorityQueue() = default;
 
 std::unique_ptr<PriorityQueue::Transaction> PriorityQueue::BeginTransaction() {
   return WrapUnique(new Transaction(this));
 }
 
 }  // namespace internal
 }  // namespace base