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..57d7254ae757c53a9d6cbe60ee1aaf28257131ec 100644
--- a/chrome/browser/resources/chromeos/login/oobe_welcome_dialog.js
+++ b/chrome/browser/resources/chromeos/login/oobe_welcome_dialog.js
@@ -19,6 +19,11 @@ Polymer({
       type: Boolean,
       value: false,
     },
+
+    languageButtonLabel_: {
+      type: String,
+      value: "languageButtonLabel",
+    },
   },
 
   onLanguageClicked_: function() {
@@ -35,5 +40,15 @@ 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);
+  },
 });