[Card unmask dialog] Prefer to translate CVC to an abbreviated form

The current CVC placeholder string is translated to the full form in
some languages and doesn't look well on the card unmask dialog (for
example, it looks like "Crypto..." in French). This adds a restraint
to the number of characters it should be translated to and add a
"meaning" tag to ensure the translation is not shared with other
properties.

Bug: 873158

Change-Id: I1ffd5154ef94705efe86dae842fbf913b09b6a36
Reviewed-on: https://chromium-review.googlesource.com/1170586
Commit-Queue: Fabio Tirelo <ftirelo@chromium.org>
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582227}

components/autofill_strings.grdp

@@ -400,7 +400,7 @@
   <message name="IDS_AUTOFILL_CARD_UNMASK_NEW_CARD_LINK" desc="Text for link that prompts user to update their credit card after it may have been re-issued." formatter_data="android_java">
     Update card
   </message>
-  <message name="IDS_AUTOFILL_DIALOG_PLACEHOLDER_CVC" desc="The placeholder/label text for credit card verification code in the requestAutocomplete dialog.">
+  <message name="IDS_AUTOFILL_DIALOG_PLACEHOLDER_CVC" desc="The placeholder/label text for credit card verification code in the requestAutocomplete dialog. The text field where this is presented can be very narrow, so please prefer to translate this to the most common abbreviated form. [CHAR-LIMIT=4]" meaning="Placeholder label for a very narrow CVC field that should preferably be translated to an abbreviated form.">
     CVC
   </message>
   <message name="IDS_AUTOFILL_LOADING_REGIONS" desc="The string to display in the regions combobox while loading the region data.">