Revert "[ios] Refactor //ios/web find_in_page.js search"

This reverts commit 5968f8fc2c5c9e3d830fe48d5a9bbd1b3ac5489f.

Reason for revert: Broken test, see crbug.com/896867

Original change's description:
> [ios] Refactor //ios/web find_in_page.js search
> 
> Changes highlightWord nomenclature to findString, and removes logic that
> searches through all child frames. Refactor pumpSearch to not highlight
> first result. findString and pumpSearch also only returns numerical value
> of matches since decision which frame to highligh/scroll to is done by
> manager.
> 
> Bug: 896867, 895529
> Change-Id: Ib71ffaffda96e20a0e0721df0085476e998ae017
> Reviewed-on: https://chromium-review.googlesource.com/c/1387045
> Reviewed-by: Eugene But <eugenebut@chromium.org>
> Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
> Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#622662}

TBR=eugenebut@chromium.org,michaeldo@chromium.org,thegreenfrog@chromium.org

Change-Id: I9c5339b5561c152c3c90d68114bfb24813053bf0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 896867, 895529
Reviewed-on: https://chromium-review.googlesource.com/c/1411336
Reviewed-by: Dominic Battré <battre@chromium.org>
Commit-Queue: Dominic Battré <battre@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622791}
3 files changed