cc: Simplify task and its derived classes.

cc/tiles/image_decode_controller.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_TILES_IMAGE_DECODE_CONTROLLER_H_
 #define CC_TILES_IMAGE_DECODE_CONTROLLER_H_
 
 #include "base/memory/ref_counted.h"
 #include "cc/playback/decoded_draw_image.h"
 #include "cc/playback/draw_image.h"
 
 namespace cc {
 
-class ImageDecodeTask;
+class Task;
 
 // ImageDecodeController is responsible for generating decode tasks, decoding
 // images, storing images in cache, and being able to return the decoded images
 // when requested.
 
 // ImageDecodeController is responsible for the following things:
 // 1. Given a DrawImage, it can return an ImageDecodeTask which when run will
 //    decode and cache the resulting image. If the image does not need a task to
 //    be decoded, then nullptr will be returned. The return value of the
 //    function indicates whether the image was or is going to be locked, so an
@@ skipping 11 matching lines @@
   virtual ~ImageDecodeController() {}
 
   // Fill in an ImageDecodeTask which will decode the given image when run. In
   // case the image is already cached, fills in nullptr. Returns true if the
   // image needs to be unreffed when the caller is finished with it.
   //
   // This is called by the tile manager (on the compositor thread) when creating
   // a raster task.
   virtual bool GetTaskForImageAndRef(const DrawImage& image,
                                      uint64_t prepare_tiles_id,
-                                     scoped_refptr<ImageDecodeTask>* task) = 0;
+                                     scoped_refptr<Task>* task) = 0;
   // Unrefs an image. When the tile is finished, this should be called for every
   // GetTaskForImageAndRef call that returned true.
   virtual void UnrefImage(const DrawImage& image) = 0;
 
   // Returns a decoded draw image. This may cause a decode if the image was not
   // predecoded.
   //
   // This is called by a raster task (on a worker thread) when an image is
   // required.
   virtual DecodedDrawImage GetDecodedImageForDraw(const DrawImage& image) = 0;
   // Unrefs an image. This should be called for every GetDecodedImageForDraw
   // when the draw with the image is finished.
   virtual void DrawWithImageFinished(const DrawImage& image,
                                      const DecodedDrawImage& decoded_image) = 0;
 
   // This function informs the controller that now is a good time to clean up
   // memory. This is called periodically from the compositor thread.
   virtual void ReduceCacheUsage() = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_IMAGE_DECODE_CONTROLLER_H_