Grid line labels disappear on update

On grid line update, the label position change is handled incorrectly.
See http://jsfiddle.net/xc8kcu8s/4/ (labels that were placed at 'start' disappear)

Re-creating the grid lines is impossible due to #1459

Start by reproducing the disappearing labels in the linked JSFiddle, focusing on grid-line updates where labels are positioned at “start.” Read issue #1459 before choosing an approach, since the report says recreating grid lines is currently impossible. Done means labels remain visible in the correct position after the update.

Written by the indexing model from the issue text.