Spoken text for [...] button on login screen

BUG=488666

Add spoken feedback but no visible text to button that leads to "Add supervised user"

Review URL: https://codereview.chromium.org/1125373004

Cr-Commit-Position: refs/heads/master@{#330532}

chrome/app/generated_resources.grd

@@ -14252,6 +14252,9 @@ After you create a new supervised user, you can manage their settings at any tim
         <message name="IDS_GO_INCOGNITO_BUTTON" desc="Text shown on Chrome OS sign-in screen button that launches guest session. Should be short.">
           Browse as Guest
         </message>
+        <message name="IDS_MORE_OPTIONS_BUTTON" desc="Text read but not shown on the [...] button on login screen">
+          More Options
+        </message>
         <message name="IDS_SCREEN_LOCK_ACTIVE_USER">
           Currently signed in
         </message>

chrome/browser/resources/chromeos/login/header_bar.html

@@ -22,7 +22,8 @@
         i18n-content="cancel" hidden></button>
   </div>
   <div id="more-settings-header-bar-item" class="header-bar-item">
-    <button id="more-settings-button" class="custom-appearance"></button>
+    <button id="more-settings-button" class="custom-appearance"
+        aria-label="moreOptions"></button>
     <button class="add-supervised-user-menu custom-appearance"
         id="add-supervised-user-menu" tabindex="0"
         i18n-content="addSupervisedUser">
@@ -35,7 +36,6 @@
   <div id="cancel-multiple-sign-in-item" class="header-bar-item" hidden>
     <button id="cancel-multiple-sign-in-button" class="custom-appearance"
         i18n-content="cancel"></button>
-    </button>
   </div>
   <div id="cancel-consumer-management-enrollment" class="header-bar-item"
       hidden>

chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc

@@ -365,6 +365,7 @@ void SigninScreenHandler::DeclareLocalizedValues(
   builder->Add("shutDown", IDS_SHUTDOWN_BUTTON);
   builder->Add("addUser", IDS_ADD_USER_BUTTON);
   builder->Add("browseAsGuest", IDS_GO_INCOGNITO_BUTTON);
+  builder->Add("moreOptions", IDS_MORE_OPTIONS_BUTTON);
   builder->Add("addSupervisedUser", IDS_CREATE_SUPERVISED_USER_MENU_LABEL);
   builder->Add("cancel", IDS_CANCEL);
   builder->Add("signOutUser", IDS_SCREEN_LOCK_SIGN_OUT);