cc: Simplify task and its derived classes.

cc/tiles/software_image_decode_controller.h

 // Copyright 2016 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_SOFTWARE_IMAGE_DECODE_CONTROLLER_H_
 #define CC_TILES_SOFTWARE_IMAGE_DECODE_CONTROLLER_H_
 
 #include <stdint.h>
 
 #include <unordered_map>
@@ skipping 85 matching lines @@
   using ImageKey = ImageDecodeControllerKey;
   using ImageKeyHash = ImageDecodeControllerKeyHash;
 
   explicit SoftwareImageDecodeController(ResourceFormat format);
   SoftwareImageDecodeController();
   ~SoftwareImageDecodeController() override;
 
   // ImageDecodeController overrides.
   bool GetTaskForImageAndRef(const DrawImage& image,
                              uint64_t prepare_tiles_id,
-                             scoped_refptr<ImageDecodeTask>* task) override;
+                             scoped_refptr<DependencyTask>* task) override;
   void UnrefImage(const DrawImage& image) override;
   DecodedDrawImage GetDecodedImageForDraw(const DrawImage& image) override;
   void DrawWithImageFinished(const DrawImage& image,
                              const DecodedDrawImage& decoded_image) override;
   void ReduceCacheUsage() override;
 
   // Decode the given image and store it in the cache. This is only called by an
   // image decode task from a worker thread.
   void DecodeImage(const ImageKey& key, const DrawImage& image);
 
@@ skipping 73 matching lines @@
   void RefAtRasterImage(const ImageKey& key);
   void UnrefAtRasterImage(const ImageKey& key);
 
   // These functions indicate whether the images can be handled and cached by
   // ImageDecodeController or whether they will fall through to Skia (with
   // exception of possibly prerolling them). Over time these should return
   // "false" in less cases, as the ImageDecodeController should start handling
   // more of them.
   bool CanHandleImage(const ImageKey& key);
 
-  std::unordered_map<ImageKey, scoped_refptr<ImageDecodeTask>, ImageKeyHash>
+  std::unordered_map<ImageKey, scoped_refptr<DependencyTask>, ImageKeyHash>
       pending_image_tasks_;
 
   // The members below this comment can only be accessed if the lock is held to
   // ensure that they are safe to access on multiple threads.
   base::Lock lock_;
 
   using ImageMRUCache =
       base::HashingMRUCache<ImageKey, scoped_ptr<DecodedImage>, ImageKeyHash>;
 
   // Decoded images and ref counts (predecode path).
@@ skipping 11 matching lines @@
   // image the first time we see it. This mimics the previous behavior and
   // should over time change as the compositor starts to handle more cases.
   std::unordered_set<uint32_t> prerolled_images_;
 
   ResourceFormat format_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_SOFTWARE_IMAGE_DECODE_CONTROLLER_H_