cr-network-select: implement focus()

ui/webui/resources/cr_elements/network/cr_network_list.js

Index: ui/webui/resources/cr_elements/network/cr_network_list.js
diff --git a/ui/webui/resources/cr_elements/network/cr_network_list.js b/ui/webui/resources/cr_elements/network/cr_network_list.js
index 82b5fc70658c3bfd4b8553983412ad5cf1e593cf..54588416fee54bd71bf5d1f3734532f10b6f7d5a 100644
--- a/ui/webui/resources/cr_elements/network/cr_network_list.js
+++ b/ui/webui/resources/cr_elements/network/cr_network_list.js
@@ -67,12 +67,46 @@ Polymer({
 
   observers: ['updateListItems_(networks, customItems)'],
 
+  /**
+    * True if element is focused, but dom-repeat is not rendered yet.
+    * @private
+    */
+  needFocus_: false,
+
+  attached: function() {
+    var self = this;
+    var observer = new MutationObserver(function() {
+      self.checkFocus_();
+    });
+    observer.observe(this.$.networkList, { childList: true });
+  },
+
+  focus: function() {
+    this.needFocus_ = false;
+    var items = this.$.networkList.getElementsByTagName('cr-network-list-item');
+    if (items && items[0]) {
+      items[0].focus();
+    } else {
+      this.needFocus_ = true;
+    }
+  },
+
+  /**
+    * Triggers delayed focus.
+    * @private
+    */
+  checkFocus_: function() {
+    if (this.needFocus_)
+      this.focus();
+  },
+
   /** @private */
   updateListItems_: function() {
     this.saveScroll(this.$.networkList);
     this.listItems_ = this.networks.concat(this.customItems);
     this.restoreScroll(this.$.networkList);
     this.updateScrollableContents();
+    this.checkFocus_();
   },
 
   /**