Chrome OS OOBE: Implement propagateUpdateLocalizedContent().

This CL adds OobeDialogHostBehavior::propagateUpdateLocalizedContent to
notify multilayer oobe-dialog structures of the locale change.

Bug: 828999
Change-Id: I86432fc41a12ddf50f94228aaab27e23332eb982
Reviewed-on: https://chromium-review.googlesource.com/1188487Reviewed-by: Wenzhao (Colin) Zang <wzang@chromium.org>
Commit-Queue: Alexander Alekseev <alemate@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585990}

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

@@ -48,6 +48,24 @@ var OobeDialogHostBehavior = {
 
     this.propagateFullScreenMode();
   },
+
+  /**
+   * Triggers updateLocalizedContent() for elements matched by |selector|.
+   * @param {string} selector CSS selector.
+   */
+  propagateUpdateLocalizedContent: function(selector) {
+    if (!selector)
+      selector = 'oobe-dialog';
+
+    var screens = Polymer.dom(this.root).querySelectorAll(selector);
+    for (var i = 0; i < screens.length; ++i) {
+      screens[i].updateLocalizedContent();
+    }
+  },
+
+  updateLocalizedContent: function() {
+    this.propagateUpdateLocalizedContent();
+  },
 };
 
 /**