Performance test for deeply nested tables inside multicol.

This is similar to printing deeply nested tables, and we have serious
performance issues with this.

Landing the performance test separately from the actual fix, so that we can
observe the improvement when the fix eventually lands.

BUG=487026

Review-Url: https://chromiumcodereview.appspot.com/1695193006
Cr-Commit-Position: refs/heads/master@{#426461}
1 file changed