Web content context menu shows over chrome://bookmarks menu.

ui/webui/resources/js/cr/ui/menu_button.js

 // Copyright (c) 2012 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.
 
 // <include src="../../assert.js">
 
 cr.exportPath('cr.ui');
 
 /**
  * Enum for type of hide. Delayed is used when called by clicking on a
@@ skipping 136 matching lines @@
           this.hideMenu(hideDelayed ? HideType.DELAYED : HideType.INSTANT);
           break;
         case 'scroll':
           if (!(e.target == this.menu || this.menu.contains(e.target)))
             this.hideMenu();
           break;
         case 'popstate':
         case 'resize':
           this.hideMenu();
           break;
+        case 'contextmenu':
+          if ((!this.menu || !this.menu.contains(e.target)) &&
+              (!this.hideTimestamp_ || Date.now() - this.hideTimestamp_ > 50))
+            this.showMenu(true);
+          e.preventDefault();
+          // Don't allow elements further up in the DOM to show their menus.
+          e.stopPropagation();
+          break;
       }
     },
 
     /**
      * Shows the menu.
      * @param {boolean} shouldSetFocus Whether to set focus on the
      *     selected menu item.
      */
     showMenu: function(shouldSetFocus) {
       this.hideMenu();
@@ skipping 12 matching lines @@
 
       // When the menu is shown we steal all keyboard events.
       var doc = this.ownerDocument;
       var win = doc.defaultView;
       this.showingEvents_.add(doc, 'keydown', this, true);
       this.showingEvents_.add(doc, 'mousedown', this, true);
       this.showingEvents_.add(doc, 'focus', this, true);
       this.showingEvents_.add(doc, 'scroll', this, true);
       this.showingEvents_.add(win, 'popstate', this);
       this.showingEvents_.add(win, 'resize', this);
+      this.showingEvents_.add(this.menu, 'contextmenu', this);
       this.showingEvents_.add(this.menu, 'activate', this);
       this.positionMenu_();
 
       if (shouldSetFocus)
         this.menu.focusSelectedItem();
     },
 
     /**
      * Hides the menu. If your menu can go out of scope, make sure to call this
      * first.
      * @param {cr.ui.HideType=} opt_hideType Type of hide.
      *     default: cr.ui.HideType.INSTANT.
      */
     hideMenu: function(opt_hideType) {
       if (!this.isMenuShown())
         return;
 
       this.removeAttribute('menu-shown');
       if (opt_hideType == HideType.DELAYED)
         this.menu.classList.add('hide-delayed');
       else
         this.menu.classList.remove('hide-delayed');
       this.menu.hidden = true;
 
       this.showingEvents_.removeAll();
       this.focus();
+
+      // On windows we might hide the menu in a right mouse button up and if
+      // that is the case we wait some short period before we allow the menu
+      // to be shown again.
+      this.hideTimestamp_ = cr.isWindows ? Date.now() : 0;
     },
 
     /**
      * Whether the menu is shown.
      */
     isMenuShown: function() {
       return this.hasAttribute('menu-shown');
     },
 
     /**
@@ skipping 74 matching lines @@
         'drop-down-arrow-hover', ARROW_WIDTH, ARROW_HEIGHT, opt_hoverColor);
     createDropDownArrowCanvas(
         'drop-down-arrow-active', ARROW_WIDTH, ARROW_HEIGHT, opt_activeColor);
   };
 
   // Export
   return {
     MenuButton: MenuButton,
   };
 });