MenuRunner: Add comment to specify blocking behavior on MacViews.

ui/views/controls/menu/menu_runner.h

 // 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.
 
 #ifndef UI_VIEWS_CONTROLS_MENU_MENU_RUNNER_H_
 #define UI_VIEWS_CONTROLS_MENU_MENU_RUNNER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 90 matching lines @@
     // Indicates RunMenuAt is returning because the MenuRunner was deleted.
     MENU_DELETED,
 
     // Indicates RunMenuAt returned and MenuRunner was not deleted.
     NORMAL_EXIT
   };
 
   // Creates a new MenuRunner, which may use a native menu if available.
   // |run_types| is a bitmask of RunTypes. If provided,
   // |on_menu_closed_callback| is invoked when the menu is closed.
+  // Note that with a native menu (e.g. on Mac), the ASYNC flag in |run_types|
+  // may be ignored. See http://crbug.com/682544.
   MenuRunner(ui::MenuModel* menu_model,
              int32_t run_types,
              const base::Closure& on_menu_closed_callback = base::Closure());
 
   // Creates a runner for a custom-created toolkit-views menu.
   MenuRunner(MenuItemView* menu, int32_t run_types);
   ~MenuRunner();
 
   // Runs the menu. If this returns MENU_DELETED the method is returning
   // because the MenuRunner was deleted.
@@ skipping 52 matching lines @@
 
  protected:
   DisplayChangeListener() {}
 };
 
 }  // namespace internal
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_MENU_MENU_RUNNER_H_