Add a UseCounter for listened 'search' events

Bug: 690143
Change-Id: Ie200f5d11b043db1681f2c40ccb99b92376faabf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1529980
Reviewed-by: Hayato Ito <hayato@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641950}
3 files changed