New badge on Add to Group... menu

Requested by PM to be symmetric with "Add to new group" menu.

Bug: 1117460

Change-Id: I4c1047e076b889cd122e18da74187324419ed391
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2363394Reviewed-by: Collin Baker <collinbaker@chromium.org>
Commit-Queue: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/master@{#799823}

chrome/browser/ui/tabs/tab_menu_model.cc

@@ -50,6 +50,7 @@ void TabMenuModel::Build(TabStripModel* tab_strip, int index) {
                  l10n_util::GetPluralStringFUTF16(
                      IDS_TAB_CXMENU_ADD_TAB_TO_GROUP, num_affected_tabs),
                  add_to_existing_group_submenu_.get());
+      SetIsNewFeatureAt(GetItemCount() - 1, true);
     } else {
       AddItem(TabStripModel::CommandAddToNewGroup,
               l10n_util::GetPluralStringFUTF16(