scheduler: Maintain a constant enqueue order for every task

third_party/WebKit/Source/platform/scheduler/base/work_queue.h

 // Copyright 2015 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 THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_WORK_QUEUE_H_
 #define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_WORK_QUEUE_H_
 
 #include <stddef.h>
 
 #include <set>
@@ skipping 80 matching lines @@
 
   // Test support function. This should not be used in production code.
   void PopTaskForTest();
 
   // Returns true if the front task in this queue has an older enqueue order
   // than the front task of |other_queue|. Both queue are assumed to be
   // non-empty. This method ignores any fences.
   bool ShouldRunBefore(const WorkQueue* other_queue) const;
 
   // Submit a fence. When TakeTaskFromWorkQueue encounters a task whose
-  // enqueue_order is >= |fence| then the WorkQueue will start pretending to be.
-  // empty.
+  // sequence number is >= |fence| then the WorkQueue will start pretending to
+  // be. empty.
   // Inserting a fence may supersede a previous one and unblock some tasks.
   // Returns true if any tasks where unblocked, returns false otherwise.
-  bool InsertFence(EnqueueOrder fence);
+  bool InsertFence(SequenceNumber fence);
 
   // Removes any fences that where added and if WorkQueue was pretending to be
   // empty, then the real value is reported to WorkQueueSets. Returns true if
   // any tasks where unblocked.
   bool RemoveFence();
 
   // Returns true if any tasks are blocked by the fence. Returns true if the
   // queue is empty and fence has been set (i.e. future tasks would be blocked).
   // Otherwise returns false.
   bool BlockedByFence() const;
 
  private:
   WTF::Deque<TaskQueueImpl::Task> work_queue_;
   WorkQueueSets* work_queue_sets_;   // NOT OWNED.
   TaskQueueImpl* const task_queue_;  // NOT OWNED.
   size_t work_queue_set_index_;
   HeapHandle heap_handle_;
   const char* const name_;
-  EnqueueOrder fence_;
+  SequenceNumber fence_;
   const QueueType queue_type_;
 
   DISALLOW_COPY_AND_ASSIGN(WorkQueue);
 };
 
 }  // namespace internal
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_WORK_QUEUE_H_