The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/810bd94c518d964856c7b25fde729645fae6336d

commit 810bd94c518d964856c7b25fde729645fae6336d
Author: Eugene But <eugenebut@chromium.org>
Date: Mon Feb 26 16:05:53 2018

Localize New Download Manager strings.

Reused existing strings where possible added new strings to grit file
for translation.

Bug:  805533 
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I0d38ddfe0ccec27c9c3f28cb04e9717b983d650c
Reviewed-on: https://chromium-review.googlesource.com/935447
Commit-Queue: Eugene But <eugenebut@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539147}
[modify] https://crrev.com/810bd94c518d964856c7b25fde729645fae6336d/ios/chrome/app/strings/ios_strings.grd
[modify] https://crrev.com/810bd94c518d964856c7b25fde729645fae6336d/ios/chrome/browser/ui/download/download_manager_coordinator.mm
[modify] https://crrev.com/810bd94c518d964856c7b25fde729645fae6336d/ios/chrome/browser/ui/download/download_manager_view_controller.mm
[modify] https://crrev.com/810bd94c518d964856c7b25fde729645fae6336d/ios/chrome/browser/ui/download/download_manager_view_controller_unittest.mm

Verified the issue on 67.0.3363.0 canary tested on iPhone 7+(iOS 11.2.6).
New download Manager strings are localized tested on Arabic and Chinese languages, works fine.

Enabled "Use new download manager UI" from chrome://flags