Reference CL for the new task scheduler.

base/task_scheduler/sequence.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/sequence.h"
+
+#include <utility>
+
+#include "base/logging.h"
+
+namespace base {
+namespace internal {
+
+Sequence::Sequence() : num_tasks_per_priority_() {}
+
+void Sequence::PushTask(scoped_ptr<Task> task, size_t* prev_num_tasks) {
+  AutoSchedulerLock auto_lock(lock_);
+
+  ++num_tasks_per_priority_[static_cast<TaskPriorityUnderlyingType>(
+      task->traits.priority())];
+  *prev_num_tasks = queue_.size();
+  queue_.push(std::move(task));
+}
+
+const Task* Sequence::PeekTask() {
+  AutoSchedulerLock auto_lock(lock_);
+
+  if (queue_.empty())
+    return nullptr;
+
+  return queue_.front().get();
+}
+
+void Sequence::PopTask(size_t* new_num_tasks) {
+  DCHECK(new_num_tasks);
+  AutoSchedulerLock auto_lock(lock_);
+  DCHECK(!queue_.empty());
+
+  --num_tasks_per_priority_[static_cast<TaskPriorityUnderlyingType>(
+      queue_.front()->traits.priority())];
+  queue_.pop();
+  *new_num_tasks = queue_.size();
+}
+
+SequenceSortKey Sequence::GetSortKey() {
+  AutoSchedulerLock auto_lock(lock_);
+  DCHECK(!queue_.empty());
+
+  // Find the highest task priority in the sequence.
+  TaskPriority priority = TaskPriority::BACKGROUND;
+  for (TaskPriorityUnderlyingType i = kNumTaskPriorities - 1; i >= 0; --i) {
+    if (num_tasks_per_priority_[i] > 0) {
+      priority = static_cast<TaskPriority>(i);
+      break;
+    }
+  }
+
+  return SequenceSortKey(priority, queue_.front()->post_time);
+}
+
+Sequence::~Sequence() = default;
+
+}  // namespace internal
+}  // namespace base