cc: Move pre-decodes to background worker.

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 86c66c4446efabb3b165138ebc0220b0ab5dca5b..f8d979d3928aa915b60e415516a6da20850b49bb 100644
--- a/cc/tiles/tile_manager.h
+++ b/cc/tiles/tile_manager.h
@@ -332,7 +332,7 @@ class CC_EXPORT TileManager : CheckerImageTrackerClient {
   scoped_refptr<TileTask> CreateTaskSetFinishedTask(
       void (TileManager::*callback)());
   PrioritizedWorkToSchedule AssignGpuMemoryToTiles();
-  void ScheduleTasks(const PrioritizedWorkToSchedule& work_to_schedule);
+  void ScheduleTasks(PrioritizedWorkToSchedule work_to_schedule);
 
   void PartitionImagesForCheckering(const PrioritizedTile& prioritized_tile,
                                     const gfx::ColorSpace& raster_color_space,
@@ -341,6 +341,7 @@ class CC_EXPORT TileManager : CheckerImageTrackerClient {
   void AddCheckeredImagesToDecodeQueue(
       const PrioritizedTile& prioritized_tile,
       const gfx::ColorSpace& raster_color_space,
+      CheckerImageTracker::DecodeType decode_type,
       CheckerImageTracker::ImageDecodeQueue* image_decode_queue);
 
   std::unique_ptr<base::trace_event::ConvertableToTraceFormat>