Will be used for UMA to track time spent optimizing code in the wild.

Change-Id: Ibc01540552eac4cb9224f1cb6cc11a55aae5834d
Reviewed-on: https://chromium-review.googlesource.com/444345Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43374}