Log the selected omnibox position when starting the app.

(cherry picked from commit 00d351477d9c7ef8b08c2727d3d329843e7a0882)

Bug: 1496338
Change-Id: Ie00a1b13f9177311ee4875dcd6827eafd6809bf8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4979887
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Christian Xu <christianxu@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Auto-Submit: Christian Xu <christianxu@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1216089}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4987636
Reviewed-by: Erhu Akpobaro <eakpobaro@google.com>
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Cr-Commit-Position: refs/branch-heads/6045@{#1289}
Cr-Branched-From: 905e8bdd32d891451d94d1ec71682e989da2b0a1-refs/heads/main@{#1204232}