Add UMA histograms for Overlay Processor

Change-Id: Ifb9d930de489d058bc10fe98172fef72c8e864de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1524990
Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Maggie Chen <magchen@chromium.org>
Commit-Queue: Mark Yacoub <markyacoub@google.com>
Cr-Commit-Position: refs/heads/master@{#643087}
1 file changed