[ios] Fix Max String Length for Clear Browsing Data Button in History

In some languages, the translation is too long for the bottom toolbar to fit it and the "edit" button without truncating. Since we have little control over BarButtonItems, we should cap the length at 16em to allow for both to be readable.

Bug: 841289
Change-Id: I19e76002baac55c2ed3099e54dfb504862662597
Reviewed-on: https://chromium-review.googlesource.com/1148996Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577932}

components/history_strings.grdp

@@ -51,7 +51,7 @@
     No search results found
   </message>
   <if expr="not use_titlecase">
-  <message name="IDS_HISTORY_OPEN_CLEAR_BROWSING_DATA_DIALOG" desc="Title of the button that will open the clear browsing data dialog.">
+  <message name="IDS_HISTORY_OPEN_CLEAR_BROWSING_DATA_DIALOG" desc="Title of the button that will open the clear browsing data dialog [Length: 16em].">
     Clear browsing data...
   </message>
   </if>