cc: Simplify Task and its derived classes.

cc/tiles/tile_manager.h

Index: cc/tiles/tile_manager.h
diff --git a/cc/tiles/tile_manager.h b/cc/tiles/tile_manager.h
index 37f30998570ecae241c104cdb452b00cb3cc2b05..a5349c440278be569a2e3ad3291fae654168b774 100644
--- a/cc/tiles/tile_manager.h
+++ b/cc/tiles/tile_manager.h
@@ -18,7 +18,6 @@
 #include "base/values.h"
 #include "cc/base/unique_notifier.h"
 #include "cc/playback/raster_source.h"
-#include "cc/raster/tile_task_runner.h"
 #include "cc/raster/tile_task_worker_pool.h"
 #include "cc/resources/memory_history.h"
 #include "cc/resources/resource_pool.h"
@@ -249,8 +248,7 @@ class CC_EXPORT TileManager {
 
   void FreeResourcesForTile(Tile* tile);
   void FreeResourcesForTileAndNotifyClientIfTileWasReadyToDraw(Tile* tile);
-  scoped_refptr<RasterTask> CreateRasterTask(
-      const PrioritizedTile& prioritized_tile);
+  scoped_refptr<Task> CreateRasterTask(const PrioritizedTile& prioritized_tile);
 
   std::unique_ptr<EvictionTilePriorityQueue>
   FreeTileResourcesUntilUsageIsWithinLimit(
@@ -277,7 +275,7 @@ class CC_EXPORT TileManager {
   void DidFinishRunningTileTasksRequiredForDraw();
   void DidFinishRunningAllTileTasks();
 
-  scoped_refptr<TileTask> CreateTaskSetFinishedTask(
+  scoped_refptr<Task> CreateTaskSetFinishedTask(
       void (TileManager::*callback)());
 
   std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
@@ -307,12 +305,12 @@ class CC_EXPORT TileManager {
 
   std::vector<Tile*> released_tiles_;
 
-  std::vector<scoped_refptr<TileTask>> orphan_tasks_;
+  Task::Vector orphan_tasks_;
 
   TaskGraph graph_;
-  scoped_refptr<TileTask> required_for_activation_done_task_;
-  scoped_refptr<TileTask> required_for_draw_done_task_;
-  scoped_refptr<TileTask> all_done_task_;
+  scoped_refptr<Task> required_for_activation_done_task_;
+  scoped_refptr<Task> required_for_draw_done_task_;
+  scoped_refptr<Task> all_done_task_;
 
   UniqueNotifier more_tiles_need_prepare_check_notifier_;