Compute all webview find options before cloning them

In WebViewFindHelper::Find, we're cloning the find options before we've
set the value for `new_session`. For requests that are part of the same
session, in WebViewFindHelper::FindReply, we're using the incorrect
value for `new_session` and we're destroying the FindInfo for what we
think is a previous session but is actually for the request we're
currently processing.

We now fully compute the options before cloning them.

Bug: 1443401
Change-Id: Ife6747aedabaf74f9a4855a173349ffe612b6f95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4533923
Reviewed-by: James Maclean <wjmaclean@chromium.org>
Commit-Queue: James Maclean <wjmaclean@chromium.org>
Auto-Submit: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1145265}