Wrap IDS_SETTINGS_SEARCH_ENGINES_QUERY_URL_EXPLANATION %s in a <ph> element

This IDS string contains a "%s" substring. Ensure the substring is not
localized: wrap the "%s" substring in an i18n <ph> placeholder element,
which ensures translators can't modify it.

No change in behavior, no new tests.

Bug: 920577
Change-Id: I1afafd2d943c20cd7aa9c418e9309d3f54d2b7b8
Reviewed-on: https://chromium-review.googlesource.com/c/1404905
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622279}
1 file changed