cc: Simplify the logic for deciding to update tile priorities.

cc/picture_layer_tiling.cc

Index: cc/picture_layer_tiling.cc
diff --git a/cc/picture_layer_tiling.cc b/cc/picture_layer_tiling.cc
index fbeb89aefee83ea008c67ab50b47504a9becda49..8e9559ca9308465a8870a344eab0993403a1eaae 100644
--- a/cc/picture_layer_tiling.cc
+++ b/cc/picture_layer_tiling.cc
@@ -364,20 +364,8 @@ void PictureLayerTiling::UpdateTilePriorities(
   if (ContentRect().IsEmpty())
     return;
 
-  bool first_update_in_new_source_frame =
-      current_source_frame_number != last_source_frame_number_;
-
-  bool first_update_in_new_impl_frame =
-      current_frame_time != last_impl_frame_time_;
-
-  // In pending tree, this is always called. We update priorities:
-  // - Immediately after a commit (first_update_in_new_source_frame).
-  // - On animation ticks after the first frame in the tree
-  //   (first_update_in_new_impl_frame).
-  // In active tree, this is only called during draw. We update priorities:
-  // - On draw if properties were not already computed by the pending tree
-  //   and activated for the frame (first_update_in_new_impl_frame).
-  if (!first_update_in_new_impl_frame && !first_update_in_new_source_frame)
+  if (!needs_update_tile_priorities(current_source_frame_number,
+                                    current_frame_time))
     return;
 
   double time_delta = 0;