This test checks the performance benefits of CSS-Contain on a spreadsheet like situation.
The page contains 10,000 auto-sized DOM nodes, placed in a 100 column grid with auto sized columns. Clicking "Update" replaces the content of the textNode of each DOM node with a random number. This requires a full relayout. Making the nodes fixed size and applying contain:strict should make an update go significantly faster, since a full relayout should not be necessary.
Just to be sure this isn't triggering anything grid specific, you can turn off grid, and be left with 10,000 inline-blocks. The same logic should apply.

Grid Fixed size Use "contain:strict"