Do not call event.preventDefault() on touchstart for menu items.

ui/webui/resources/js/cr/ui/context_menu_handler.js

Index: ui/webui/resources/js/cr/ui/context_menu_handler.js
diff --git a/ui/webui/resources/js/cr/ui/context_menu_handler.js b/ui/webui/resources/js/cr/ui/context_menu_handler.js
index fd9b183b341a0ce2aaeb15e798a5d0297e597081..710856b1528f61f617eb31567ca7d98e811cb506 100644
--- a/ui/webui/resources/js/cr/ui/context_menu_handler.js
+++ b/ui/webui/resources/js/cr/ui/context_menu_handler.js
@@ -151,12 +151,17 @@ cr.define('cr.ui', function() {
 
       switch (e.type) {
         case 'mousedown':
-        case 'touchstart':
           if (!this.menu.contains(e.target))
             this.hideMenu();
           else
             e.preventDefault();
           break;
+
+        case 'touchstart':
+          if (!this.menu.contains(e.target))
+            this.hideMenu();
+          break;
+
         case 'keydown':
           // keyIdentifier does not report 'Esc' correctly
           if (e.keyCode == 27 /* Esc */) {