TaskGraphRunner refactor

cc/raster/synchronous_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_SYNCHRONOUS_TASK_GRAPH_RUNNER_H_
+#define CC_RASTER_SYNCHRONOUS_TASK_GRAPH_RUNNER_H_
+
+#include "cc/raster/task_graph_runner.h"
+#include "cc/raster/task_graph_work_queue.h"
+
+namespace cc {
+
+// Implements a TaskGraphRunner which runs synchronously. This runner only runs
+// tasks when RunUntilIdle is called.
+class CC_EXPORT SynchronousTaskGraphRunner : public TaskGraphRunner {
+ public:
+  SynchronousTaskGraphRunner();
+  ~SynchronousTaskGraphRunner() override;
+
+  // Overridden from TaskGraphRunner:
+  void ScheduleTasks(NamespaceToken token, TaskGraph* graph) override;
+  void WaitForTasksToFinishRunning(NamespaceToken token) override;
+  void CollectCompletedTasks(NamespaceToken token,
+                             Task::Vector* completed_tasks) override;
+
+  // Runs all pending tasks from all namespaces.
+  void RunUntilIdle();
+
+ private:
+  void RunTask();
+
+  // Stores the actual tasks to be run, sorted by priority.
+  TaskGraphWorkQueue work_queue_;
+};
+
+}  // namespace cc
+
+#endif  // CC_RASTER_SYNCHRONOUS_TASK_GRAPH_RUNNER_H_