[ios] Add Translate Modal language TextField hint

Bug: 1014959
Change-Id: I55606e3ddd0a5321df014691a07b382b3c70f1a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1918186Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715821}

ios/chrome/app/strings/ios_strings.grd

@@ -1984,6 +1984,9 @@ New Search
       <message name="IDS_IOS_TRANSLATE_INFOBAR_MODAL_SOURCE_LANGUAGE_FIELD_NAME" desc="The text field name for the source language in the Translate Infobar modal. [iOS only]">
         From
       </message>
+      <message name="IDS_IOS_TRANSLATE_INFOBAR_MODAL_LANGUAGE_FIELD_NAME_HINT" desc="Text accompanying the language field name to indicate that the user can tap the row to show options to change the language. [iOS only]">
+        Tap to change language.
+      </message>
       <message name="IDS_IOS_TRANSLATE_INFOBAR_MODAL_SELECT_LANGUAGE_HINT" desc="Text alongside the language to indicate to the user change the language by selecting the row. [iOS only]">
         Tap to change to this language.
       </message>