WebUI: fix cr-action-menu keyboard off-by-one issue

ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js

Index: ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js
diff --git a/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js b/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js
index c68aece64c28995c68bcd39c461cc52c496d20ba..9a94cfa6204e750ccfec46c635eadf1e7ce077f2 100644
--- a/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js
+++ b/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js
@@ -131,6 +131,10 @@ Polymer({
     var focusedIndex =
         Array.prototype.indexOf.call(this.options_, this.root.activeElement);
 
+    // Handle case where nothing is focused and up is pressed.
+    if (focusedIndex === -1 && step === -1)
+      focusedIndex = 0;
+
     do {
       focusedIndex = (numOptions + focusedIndex + step) % numOptions;
       nextOption = this.options_[focusedIndex];