Convert WindowOpenDisposition to an enum class.

chrome/browser/ui/cocoa/omnibox/omnibox_view_mac.mm

 // 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.
 
 #include "chrome/browser/ui/cocoa/omnibox/omnibox_view_mac.h"
 
 #include <Carbon/Carbon.h>  // kVK_Return
 
 #include "base/mac/foundation_util.h"
 #include "base/memory/ptr_util.h"
@@ skipping 861 matching lines @@
     // Opening a URL in a background tab should also revert the omnibox contents
     // to their original state.  We cannot do a blanket revert in OpenURL()
     // because middle-clicks also open in a new background tab, but those should
     // not revert the omnibox text.
     RevertAll();
     return true;
   }
 
   // Option-Return
   if (cmd == @selector(insertNewlineIgnoringFieldEditor:)) {
-    model()->AcceptInput(NEW_FOREGROUND_TAB, false);
+    model()->AcceptInput(WindowOpenDisposition::NEW_FOREGROUND_TAB, false);
     return true;
   }
 
   // When the user does Control-Enter, the existing content has "www."
   // prepended and ".com" appended.  model() should already have
   // received notification when the Control key was depressed, but it
   // is safe to tell it twice.
   if (cmd == @selector(insertLineBreak:)) {
     OnControlKeyChanged(true);
     WindowOpenDisposition disposition =
@@ skipping 246 matching lines @@
                               display_text);
   NSDictionary* notification_info = @{
       NSAccessibilityAnnouncementKey : announcement,
       NSAccessibilityPriorityKey :     @(NSAccessibilityPriorityHigh)
   };
   NSAccessibilityPostNotificationWithUserInfo(
       [field_ window],
       NSAccessibilityAnnouncementRequestedNotification,
       notification_info);
 }