ChromeOS OOBE: Add ARIA-labels for OOBE screens.

chrome/browser/resources/chromeos/login/oobe_welcome_dialog.js

Index: chrome/browser/resources/chromeos/login/oobe_welcome_dialog.js
diff --git a/chrome/browser/resources/chromeos/login/oobe_welcome_dialog.js b/chrome/browser/resources/chromeos/login/oobe_welcome_dialog.js
index 87cc78a6e48945009b41ebf5cd514ed639a53194..da888ecdc66b912b8a7f34afbcd19ba28b863a83 100644
--- a/chrome/browser/resources/chromeos/login/oobe_welcome_dialog.js
+++ b/chrome/browser/resources/chromeos/login/oobe_welcome_dialog.js
@@ -35,5 +35,15 @@ Polymer({
 
   onNextClicked_: function() {
     this.fire('next-button-clicked');
-  }
+  },
+
+  /**
+    * This function formats message for labels.
+    * @param String label i18n string ID.
+    * @param String parameter i18n string parameter.
+    * @private
+    */
+  formatMessage_: function(label, parameter) {
+    return loadTimeData.getStringF(label, parameter);
+  },
 });