Stop blocking the mousedown event of left click when closing context menu.

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 ce31f6517b5021a2f723028df2e1b5a2805e0809..ab07f6c19d7e4d050b7a7cfca03fc8282db3d9f3 100644
--- a/ui/webui/resources/js/cr/ui/context_menu_handler.js
+++ b/ui/webui/resources/js/cr/ui/context_menu_handler.js
@@ -154,7 +154,9 @@ cr.define('cr.ui', function() {
         case 'mousedown':
           if (!this.menu.contains(e.target)) {
             this.hideMenu();
-            if (e.button == 0 /* Left click */) {
+            if (e.button == 0 /* Left button */ && (cr.isLinux || cr.isMac)) {
+              // Emulate Mac and Linux, which swallow native 'mousedown' events
+              // that close menus.
               e.preventDefault();
               e.stopPropagation();
             }