[ios] Copy Find in Page JS from //ios/browser to //ios/web

Copy entire JS logic so that diffing changes to code that already
existed is easier for reviewers. Add bug numbers back to old todos.

Bug: 896867
Change-Id: I016cfbb2c7a921f33440be2f83fdb6147f69ad72
Reviewed-on: https://chromium-review.googlesource.com/c/1383578
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#617904}
2 files changed