GitLab

This add a metric for tracking time spent painting the TabStrip at a
high level and another for time spent painting TabIcons. The former is
logged for each frame the TabStrip paints. The latter is logged every
time a TabIcon paints, which can be more often since they sometimes
paint to their own layers.

These metrics are high-level and not super actionable on their own;
they are mainly intended to catch regressions.

Change-Id: Ie90f5db94ffab163aaf475c19ea678276db3b308
Bug: 966237
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1626169
Commit-Queue: Collin Baker <collinbaker@chromium.org>
Auto-Submit: Collin Baker <collinbaker@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665003}