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

preventDefault() on 'touchstart' prevents tap operation from dispatching click-like events.
On 'touchstart', preventDefault() should not be called.

BUG=374177
TEST=manually tested

Review URL: https://codereview.chromium.org/284233007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271204 0039d316-1c4b-4281-b951-d872f2087c98

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 */) {