Prevent file picker from closing lens upload dialog

The issue was caused from https://chromium-review.googlesource.com/c/chromium/src/+/4087385, which closes the upload dialog during focusOut events if the relatedTarget is null (which happens when the file picker is open). To fix this, we can make sure the document has focus (which it doesn't when the file picker is opened) before closing.

Screencast of fix and helpful console logs: https://screencast.googleplex.com/cast/NTYzMzE3ODU1NjQzMjM4NHxmNWYyNmJkYy1iNg

Bug: 1406771, b/273961108
Change-Id: I87be5930ba1bb19264af4a03140ecb24f4fe4c38
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4338401


Commit-Queue: Anthony Carrington <acarrington@google.com>
Reviewed-by: Roman Arora <romanarora@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1118921}