TaskScheduler: Add PriorityQueue::Transaction::PushNoWakeUp().

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 38 matching lines @@
   //
   // A WorkerThread needs to be able to Peek sequences from both its
   // PriorityQueues (single-threaded and shared) and then Pop the sequence with
   // the highest priority. If the Peek and the Pop are done through the same
   // Transaction, it is guaranteed that the PriorityQueue hasn't changed between
   // the 2 operations.
   class BASE_EXPORT Transaction : public NonThreadSafe {
    public:
     ~Transaction();
 
-    // Inserts |sequence_and_sort_key| in the PriorityQueue.
+    // Inserts |sequence_and_sort_key| in the PriorityQueue. Each call to this
+    // method will result in one invocation of the wake up callback when the
+    // Transaction is destroyed.
     void Push(std::unique_ptr<SequenceAndSortKey> sequence_and_sort_key);
 
+    // Inserts |sequence_and_sort_key| in the PriorityQueue without invoking the
+    // wake up callback.
+    void PushNoWakeUp(
+        std::unique_ptr<SequenceAndSortKey> sequence_and_sort_key);
+
     // Returns the SequenceAndSortKey with the highest priority or a null
     // SequenceAndSortKey if the PriorityQueue is empty. The reference becomes
     // invalid the next time that a Sequence is popped from the PriorityQueue.
     const SequenceAndSortKey& Peek() const;
 
     // Removes the SequenceAndSortKey with the highest priority from the
     // PriorityQueue. Cannot be called on an empty PriorityQueue.
     void Pop();
 
    private:
     friend class PriorityQueue;
 
     explicit Transaction(PriorityQueue* outer_queue);
 
     // Holds the lock of |outer_queue_| for most of the lifetime of this
     // Transaction. Using a scoped_ptr allows the destructor to release the lock
     // before performing internal operations which have to be done outside of
     // its scope.
     std::unique_ptr<AutoSchedulerLock> auto_lock_;
 
     PriorityQueue* const outer_queue_;
 
-    // Number of times that Push() has been called on this Transaction.
-    size_t num_pushed_sequences_ = 0;
+    // Number of times that the wake up callback should be invoked when this
+    // Transaction is destroyed.
+    size_t num_wake_ups_ = 0;
 
     DISALLOW_COPY_AND_ASSIGN(Transaction);
   };
 
-  // |sequence_inserted_callback| is a non-null callback invoked when the
-  // Transaction is done for each Push that was performed with the Transaction.
-  explicit PriorityQueue(const Closure& sequence_inserted_callback);
+  // |wake_up_callback| is a non-null callback invoked when a Transaction is
+  // done for each call to Push() on the Transaction.
+  explicit PriorityQueue(const Closure& wake_up_callback);
 
-  // |sequence_inserted_callback| is a non-null callback invoked when the
-  // Transaction is done for each Push that was performed with the Transaction.
+  // |wake_up_callback| is a non-null callback invoked when a Transaction is
+  // done for each call to Push() on the Transaction.
   // |predecessor_priority_queue| is a PriorityQueue for which a thread is
   // allowed to have an active Transaction when it creates a Transaction for
   // this PriorityQueue.
-  PriorityQueue(const Closure& sequence_inserted_callback,
+  PriorityQueue(const Closure& wake_up_callback,
                 const PriorityQueue* predecessor_priority_queue);
 
   ~PriorityQueue();
 
   // Begins a Transaction. This method cannot be called on a thread which has an
   // active Transaction unless the last Transaction created on the thread was
   // for the allowed predecessor specified in the constructor of this
   // PriorityQueue.
   std::unique_ptr<Transaction> BeginTransaction();
 
  private:
   struct SequenceAndSortKeyComparator {
     bool operator()(const std::unique_ptr<SequenceAndSortKey>& left,
                     const std::unique_ptr<SequenceAndSortKey>& right) const {
       return left->sort_key < right->sort_key;
     }
   };
   using ContainerType =
       std::priority_queue<std::unique_ptr<SequenceAndSortKey>,
                           std::vector<std::unique_ptr<SequenceAndSortKey>>,
                           SequenceAndSortKeyComparator>;
 
   // Synchronizes access to |container_|.
   SchedulerLock container_lock_;
 
   ContainerType container_;
 
-  const Closure sequence_inserted_callback_;
+  const Closure wake_up_callback_;
 
   // A null SequenceAndSortKey returned by Peek() when the PriorityQueue is
   // empty.
   const SequenceAndSortKey empty_sequence_and_sort_key_;
 
   DISALLOW_COPY_AND_ASSIGN(PriorityQueue);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_PRIORITY_QUEUE_H_