ChromeOS: Update Welcome screen material design OOBE.

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

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+Polymer({
+  is: 'oobe-welcome-dialog',
+  properties: {
+    /**
+     * Currently selected system language (display name).
+     */
+    currentLanguage: {
+      type: String,
+      value: '',
+    },
+  },
+
+  onLanguageClicked_: function() {
+    this.fire('language-button-clicked');
+  },
+
+  onAccessibilityClicked_: function() {
+    this.fire('accessibility-button-clicked');
+  },
+
+  onNextClicked_: function() {
+    this.fire('next-button-clicked');
+  }
+});