Convert WindowOpenDisposition to an enum class.

ui/base/window_open_disposition.h

 // Copyright 2011 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_BASE_WINDOW_OPEN_DISPOSITION_H_
 #define UI_BASE_WINDOW_OPEN_DISPOSITION_H_
 
 #include "ui/base/ui_base_export.h"
 
 // A Java counterpart will be generated for this enum.
 // GENERATED_JAVA_ENUM_PACKAGE: org.chromium.ui
-enum WindowOpenDisposition {
+enum class WindowOpenDisposition {
   UNKNOWN,
   CURRENT_TAB,
   // Indicates that only one tab with the url should exist in the same window.
   SINGLETON_TAB,
   NEW_FOREGROUND_TAB,
   NEW_BACKGROUND_TAB,
   NEW_POPUP,
   NEW_WINDOW,
   SAVE_TO_DISK,
   OFF_THE_RECORD,
   IGNORE_ACTION,
   // Update when adding a new disposition.
-  WINDOW_OPEN_DISPOSITION_LAST = IGNORE_ACTION
+  MAX_VALUE = IGNORE_ACTION
 };
 
 namespace ui {
 
 // Translates event flags from a click on a link into the user's desired
 // window disposition.  For example, a middle click would mean to open
 // a background tab.
 UI_BASE_EXPORT WindowOpenDisposition DispositionFromClick(bool middle_button,
                                                           bool alt_key,
                                                           bool ctrl_key,
                                                           bool meta_key,
                                                           bool shift_key);
 
 // Translates event flags into what kind of disposition they represents.
 // For example, a middle click would mean to open a background tab.
 // event_flags are the flags as understood by ui::MouseEvent.
 UI_BASE_EXPORT WindowOpenDisposition DispositionFromEventFlags(int event_flags);
 
 }  // namespace ui
 
 #endif  // UI_BASE_WINDOW_OPEN_DISPOSITION_H_