Fix cr-shared-menu focus issues.

ui/webui/resources/cr_elements/cr_shared_menu/cr_shared_menu.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /** Same as paper-menu-button's custom easing cubic-bezier param. */
 var SLIDE_CUBIC_BEZIER = 'cubic-bezier(0.3, 0.95, 0.5, 1)';
 
 Polymer({
   is: 'cr-shared-menu',
 
@@ skipping 116 matching lines @@
       return;
 
     if (this.menuOpen)
       this.closeMenu();
 
     this.itemData = itemData;
     this.lastAnchor_ = anchor;
     this.$.dropdown.restoreFocusOnClose = true;
 
     var focusableChildren = Polymer.dom(this).querySelectorAll(
-        '[tabindex]:not([hidden]),button:not([hidden])');
+        '[tabindex]:not([disabled]):not([hidden]),' +
+        'button:not([disabled]):not([hidden])');
     if (focusableChildren.length > 0) {
       this.$.dropdown.focusTarget = focusableChildren[0];
       this.firstFocus_ = focusableChildren[0];
       this.lastFocus_ = focusableChildren[focusableChildren.length - 1];
     }
 
     // Move the menu to the anchor.
     this.$.dropdown.positionTarget = anchor;
     this.menuOpen = true;
   },
@@ skipping 18 matching lines @@
    * @param {CustomEvent} e
    */
   onTabPressed_: function(e) {
     if (!this.firstFocus_ || !this.lastFocus_)
       return;
 
     var toFocus;
     var keyEvent = e.detail.keyboardEvent;
     if (keyEvent.shiftKey && keyEvent.target == this.firstFocus_)
       toFocus = this.lastFocus_;
-    else if (keyEvent.target == this.lastFocus_)
+    else if (!keyEvent.shiftKey && keyEvent.target == this.lastFocus_)
       toFocus = this.firstFocus_;
 
     if (!toFocus)
       return;
 
     e.preventDefault();
     toFocus.focus();
   },
 
   /**
@@ skipping 12 matching lines @@
    * Prevent focus restoring when tapping outside the menu. This stops the
    * focus moving around unexpectedly when closing the menu with the mouse.
    * @param {CustomEvent} e
    * @private
    */
   onOverlayCanceled_: function(e) {
     if (e.detail.type == 'tap')
       this.$.dropdown.restoreFocusOnClose = false;
   },
 });