TabBox will now select hidden tabs through arrow keys.

ui/webui/resources/js/cr/ui/tabs.js

Index: ui/webui/resources/js/cr/ui/tabs.js
diff --git a/ui/webui/resources/js/cr/ui/tabs.js b/ui/webui/resources/js/cr/ui/tabs.js
index deccce91703b6198621dd4ee191061b26f149262..17eb0bf5d854daf14e86dfc8551ad413eacacec0 100644
--- a/ui/webui/resources/js/cr/ui/tabs.js
+++ b/ui/webui/resources/js/cr/ui/tabs.js
@@ -171,7 +171,13 @@ cr.define('cr.ui', function() {
       var count = this.children.length;
       var tabbox = getTabBox(this);
       var index = tabbox.selectedIndex;
-      tabbox.selectedIndex = (index + delta + count) % count;
+
+      // Select next visible tab. Does nothing if no other tabs are visible.
+      var next = index;
+      do {
+        next = (next + delta + count) % count;
+      } while (this.children[next].hidden && index != next);
+      tabbox.selectedIndex = next;
 
       // Show focus outline since we used the keyboard.
       this.focusOutlineManager_.visible = true;