cc: Simplify task and its derived classes.

cc/raster/tile_task_runner.h

Index: cc/raster/tile_task_runner.h
diff --git a/cc/raster/tile_task_runner.h b/cc/raster/tile_task_runner.h
index 5e2f7fd1c96e96b6a4806ebdaa95badc7861d146..8ebb8d10cc41600b55994654d62ea95ae2457f69 100644
--- a/cc/raster/tile_task_runner.h
+++ b/cc/raster/tile_task_runner.h
@@ -10,72 +10,11 @@
 #include <vector>
 
 #include "base/callback.h"
+#include "cc/raster/dependency_task.h"
 #include "cc/raster/task_graph_runner.h"
 #include "cc/resources/resource_format.h"
 
 namespace cc {
-class ImageDecodeTask;
-class RasterTask;
-class Resource;
-class RasterBuffer;
-
-class CC_EXPORT TileTaskClient {
- public:
-  virtual scoped_ptr<RasterBuffer> AcquireBufferForRaster(
-      const Resource* resource,
-      uint64_t resource_content_id,
-      uint64_t previous_content_id) = 0;
-  virtual void ReleaseBufferForRaster(scoped_ptr<RasterBuffer> buffer) = 0;
-
- protected:
-  virtual ~TileTaskClient() {}
-};
-
-class CC_EXPORT TileTask : public Task {
- public:
-  typedef std::vector<scoped_refptr<TileTask>> Vector;
-
-  virtual void ScheduleOnOriginThread(TileTaskClient* client) = 0;
-  virtual void CompleteOnOriginThread(TileTaskClient* client) = 0;
-
-  void WillSchedule();
-  void DidSchedule();
-  bool HasBeenScheduled() const;
-
-  void WillComplete();
-  void DidComplete();
-  bool HasCompleted() const;
-
- protected:
-  TileTask();
-  ~TileTask() override;
-
-  bool did_schedule_;
-  bool did_complete_;
-};
-
-class CC_EXPORT ImageDecodeTask : public TileTask {
- public:
-  typedef std::vector<scoped_refptr<ImageDecodeTask>> Vector;
-
- protected:
-  ImageDecodeTask();
-  ~ImageDecodeTask() override;
-};
-
-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_;
-};
 
 // This interface can be used to schedule and run tile tasks.
 // The client can call CheckForCompletedTasks() at any time to dispatch