extensions: fix focus management for all dialogs (not just options).

ui/webui/resources/js/cr/ui/node_utils.js

Index: ui/webui/resources/js/cr/ui/node_utils.js
diff --git a/ui/webui/resources/js/cr/ui/node_utils.js b/ui/webui/resources/js/cr/ui/node_utils.js
index a380670e4f31d07968325abddf25797016aa8da7..8f92e9bfe6835bfad0d8cf81ae5f4fde47aac4d0 100644
--- a/ui/webui/resources/js/cr/ui/node_utils.js
+++ b/ui/webui/resources/js/cr/ui/node_utils.js
@@ -31,3 +31,28 @@ cr.ui.reverseButtonStrips = function(opt_root) {
     buttonStrip.setAttribute('reversed', '');
   }
 };
+
+/**
+ * Finds a good place to set initial focus. Generally called when UI is shown.
+ * @param {!Element} root Where to start looking for focusable controls.
+ * @param {string=} opt_extraFocusable A selector for extra focusable items
+ *     (e.g. '.my-link-class, [tabindex=0]').
+ */
+cr.ui.setInitialFocus = function(root, opt_extraFocusable) {
+  // Do not change focus if any element in |root| is already focused.
+  if (root.contains(document.activeElement))
+    return;
+
+  var focusableSelector = 'input, list, select, textarea, button';
+  if (opt_extraFocusable)
+    focusableSelector = opt_extraFocusable + ', ' + focusableSelector;
+
+  var elements = root.querySelectorAll(focusableSelector);
+  for (var i = 0; i < elements.length; i++) {
+    var element = elements[i];
+    element.focus();
+    // .focus() isn't guaranteed to work. Continue until it does.
+    if (document.activeElement == element)
+      return;
+  }
+};