cc: Reset tile priority before deleting tiling.

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 816a79b22b949d30e73a73a98a8516c52e03f9d0..5edf6f86024552956fb9cbcefda808383e81f929 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -458,6 +458,12 @@ scoped_refptr<Tile> PictureLayerImpl::CreateTile(PictureLayerTiling* tiling,
       is_using_lcd_text_));
 }
 
+void PictureLayerImpl::DestroyTile(Tile* tile) {
+  WhichTree tree =
+      layer_tree_impl()->IsActiveTree() ? ACTIVE_TREE : PENDING_TREE;
+  tile->SetPriority(tree, TilePriority());
+}
+
 void PictureLayerImpl::UpdatePile(Tile* tile) {
   tile->set_picture_pile(pile_);
 }