cc: Simplify Task and its derived classes.

cc/tiles/software_image_decode_controller.h

Index: cc/tiles/software_image_decode_controller.h
diff --git a/cc/tiles/software_image_decode_controller.h b/cc/tiles/software_image_decode_controller.h
index 9acf97c27ffe57c8e7b45fb45f6d3503d355fc7b..d2a1f4be87d0c230595466ce3ed4ffcfb8d028cf 100644
--- a/cc/tiles/software_image_decode_controller.h
+++ b/cc/tiles/software_image_decode_controller.h
@@ -22,7 +22,8 @@
 #include "cc/base/cc_export.h"
 #include "cc/playback/decoded_draw_image.h"
 #include "cc/playback/draw_image.h"
-#include "cc/raster/tile_task_runner.h"
+#include "cc/raster/task.h"
+#include "cc/resources/resource_format.h"
 #include "cc/tiles/image_decode_controller.h"
 #include "skia/ext/refptr.h"
 
@@ -110,7 +111,7 @@ class CC_EXPORT SoftwareImageDecodeController
   // ImageDecodeController overrides.
   bool GetTaskForImageAndRef(const DrawImage& image,
                              uint64_t prepare_tiles_id,
-                             scoped_refptr<ImageDecodeTask>* task) override;
+                             scoped_refptr<Task>* task) override;
   void UnrefImage(const DrawImage& image) override;
   DecodedDrawImage GetDecodedImageForDraw(const DrawImage& image) override;
   void DrawWithImageFinished(const DrawImage& image,
@@ -230,7 +231,7 @@ class CC_EXPORT SoftwareImageDecodeController
                                const char* cache_name,
                                base::trace_event::ProcessMemoryDump* pmd) const;
 
-  std::unordered_map<ImageKey, scoped_refptr<ImageDecodeTask>, ImageKeyHash>
+  std::unordered_map<ImageKey, scoped_refptr<Task>, ImageKeyHash>
       pending_image_tasks_;
 
   // The members below this comment can only be accessed if the lock is held to