TaskGraphRunner refactor

cc/raster/single_thread_task_graph_runner.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 CC_RASTER_SINGLE_THREAD_TASK_GRAPH_RUNNER_H_
+#define CC_RASTER_SINGLE_THREAD_TASK_GRAPH_RUNNER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "base/synchronization/condition_variable.h"
+#include "base/threading/simple_thread.h"
+#include "cc/raster/task_graph_runner.h"
+#include "cc/raster/task_graph_work_queue.h"
+
+namespace base {
+class SimpleThread;
+}
+
+namespace cc {
+
+// Runs TaskGraphs asynchronously using a single worker thread.
+class CC_EXPORT SingleThreadTaskGraphRunner
+    : public TaskGraphRunner,
+      public base::DelegateSimpleThread::Delegate {
+ public:
+  SingleThreadTaskGraphRunner();
+  ~SingleThreadTaskGraphRunner() override;
+
+  // Overridden from TaskGraphRunner:
+  NamespaceToken GetNamespaceToken() override;
+  void ScheduleTasks(NamespaceToken token, TaskGraph* graph) override;
+  void WaitForTasksToFinishRunning(NamespaceToken token) override;
+  void CollectCompletedTasks(NamespaceToken token,
+                             Task::Vector* completed_tasks) override;
+
+  // Overridden from base::DelegateSimpleThread::Delegate:
+  void Run() override;
+
+  void Start(const std::string& thread_name,
+             const base::SimpleThread::Options& thread_options);
+  void Shutdown();
+
+ private:
+  void RunTaskWithLockAcquired();
+
+  scoped_ptr<base::SimpleThread> thread_;
+
+  // Lock to exclusively access all the following members that are used to
+  // implement the TaskRunner interfaces.
+  base::Lock lock_;
+
+  // Stores the actual tasks to be run by this runner, sorted by priority.
+  TaskGraphWorkQueue work_queue_;
+
+  // Condition variable that is waited on by Run() until new tasks are ready to
+  // run or shutdown starts.
+  base::ConditionVariable has_ready_to_run_tasks_cv_;
+
+  // Condition variable that is waited on by origin threads until a namespace
+  // has finished running all associated tasks.
+  base::ConditionVariable has_namespaces_with_finished_running_tasks_cv_;
+
+  // Set during shutdown. Tells Run() to return when no more tasks are pending.
+  bool shutdown_;
+};
+
+}  // namespace cc
+
+#endif  // CC_RASTER_SINGLE_THREAD_TASK_GRAPH_RUNNER_H_