DL: Add perf test for forced layout on locked element

This tests makes sure calling layout-inducing methods on elements that
are locked and already laid-out should be cheap (won't trigger layout
on the locked subtree).

Sample run:
Duration of executing benchmark blink_perf.display_locking: 13 seconds.

Bug: 961187
Change-Id: I9e15744915b8e7f235102b651adbe1be4f7f4cdb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1614825
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Reviewed-by: Fergal Daly <fergal@chromium.org>
Reviewed-by: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661425}
1 file changed