cc: Simplify Task and its derived classes.

cc/raster/tile_task_runner.h

-// Copyright 2014 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_TILE_TASK_RUNNER_H_
-#define CC_RASTER_TILE_TASK_RUNNER_H_
-
-#include <stdint.h>
-
-#include <vector>
-
-#include "base/callback.h"
-#include "cc/raster/task_graph_runner.h"
-#include "cc/resources/resource_format.h"
-
-namespace cc {
-
-enum TaskType : TaskTypeId {
-  TASK_TYPE_DEFAULT = kDefaultTaskTypeId,
-  TASK_TYPE_RASTER,
-  TASK_TYPE_IMAGE_DECODE,
-  TASK_TYPE_IMAGE_UPLOAD
-};
-
-class CC_EXPORT TileTask : public Task {
- public:
-  typedef std::vector<scoped_refptr<TileTask>> Vector;
-
-  void DidComplete();
-  bool HasCompleted() const;
-
- protected:
-  TileTask();
-  ~TileTask() override;
-
-  bool did_complete_;
-};
-
-class CC_EXPORT ImageDecodeTask : public TileTask {
- public:
-  typedef std::vector<scoped_refptr<ImageDecodeTask>> Vector;
-
-  // Indicates whether this ImageDecodeTask can be run at the same time as
-  // other tasks in the task graph. If false, this task will be scheduled with
-  // TASK_CATEGORY_NONCONCURRENT_FOREGROUND. The base implementation always
-  // returns true.
-  virtual bool SupportsConcurrentExecution() const;
-
-  // Returns an optional task which this task depends on. May be null.
-  const scoped_refptr<ImageDecodeTask>& dependency() { return dependency_; }
-
- protected:
-  ImageDecodeTask();
-  explicit ImageDecodeTask(scoped_refptr<ImageDecodeTask> dependency);
-  ~ImageDecodeTask() override;
-
- private:
-  scoped_refptr<ImageDecodeTask> dependency_;
-};
-
-class CC_EXPORT RasterTask : public TileTask {
- public:
-  typedef std::vector<scoped_refptr<RasterTask>> Vector;
-
-  const ImageDecodeTask::Vector& dependencies() const { return dependencies_; }
-
- protected:
-  explicit RasterTask(ImageDecodeTask::Vector* dependencies);
-  ~RasterTask() override;
-
- private:
-  ImageDecodeTask::Vector dependencies_;
-};
-
-}  // namespace cc
-
-#endif  // CC_RASTER_TILE_TASK_RUNNER_H_