[DL]: Ensure find in page doesn't find locked not searchable elements.

This patch ensures that find in page skips elements that are locked for
display and for which the context IsSearchable returns false.

IsSearchable is currently set to return false for any locked element.

R=chrishtr@chromium.org, rakina@chromium.org

Bug: 882663
Change-Id: I8e9ee9b20c7cece7f70c81b5d77da7070bb907a8
Reviewed-on: https://chromium-review.googlesource.com/c/1403914
Reviewed-by: Rakina Zata Amni <rakina@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622884}
6 files changed