base: Remove a copy of and copy ctor from SequenceAndSortKey.

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 14 matching lines @@
  public:
   // An immutable struct combining a Sequence and the sort key that determines
   // its position in a PriorityQueue.
   struct BASE_EXPORT SequenceAndSortKey {
     // Constructs a null SequenceAndSortKey.
     SequenceAndSortKey();
 
     // Constructs a SequenceAndSortKey with the given |sequence| and |sort_key|.
     SequenceAndSortKey(scoped_refptr<Sequence> sequence,
                        const SequenceSortKey& sort_key);
-
-    SequenceAndSortKey(const SequenceAndSortKey& other);

[danakj, 2016/04/19 20:11:54]

DISALLOW_COPY_AND_ASSIGN then?

[vmpstr, 2016/04/19 20:14:17]

Done. I didn't do this initially, because it's unclear to me whether this is
meant to be non-copyable or it just happens that we're currently not doing any
copies. 

-
     ~SequenceAndSortKey();
 
     // Returns true if this is a null SequenceAndSortKey.
     bool is_null() const { return !sequence; }
 
     const scoped_refptr<Sequence> sequence;
     const SequenceSortKey sort_key;

[fdoray, 2016/04/19 20:14:13]

Add:
private:
  DISALLOW_COPY_AND_ASSIGN(SequenceAndSortKey);

   };
 
   // A Transaction can perform multiple operations atomically on a
   // PriorityQueue. While a Transaction is alive, it is guaranteed that nothing
   // else will access the PriorityQueue.
   //
   // 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
@@ skipping 65 matching lines @@
   // empty.
   const SequenceAndSortKey empty_sequence_and_sort_key_;
 
   DISALLOW_COPY_AND_ASSIGN(PriorityQueue);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_PRIORITY_QUEUE_H_