mac: Delete more 10.5-only code

chrome/browser/ui/cocoa/obsolete_os.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 CHROME_BROWSER_UI_COCOA_OBSOLETE_OS_H_
-#define CHROME_BROWSER_UI_COCOA_OBSOLETE_OS_H_
-
-#include "base/mac/mac_util.h"
-#include "base/string16.h"
-
-namespace chrome {
-
-// Returns true if the OS will either be unsupported by future versions of the
-// application in the near future, or if this is the last version of the
-// application that supports the OS.
-inline bool IsOSObsoleteOrNearlySo() {
-  return base::mac::IsOSLeopardOrEarlier();
-}
-
-// Returns a localized string informing users that their OS will either soon
-// be unsupported by future versions of the application, or that they are
-// already using the last version of the application that supports their OS.
-// Do not use the returned string unless IsOSObsoleteOrNearlySo() returns
-// true.
-string16 LocalizedObsoleteOSString();
-
-}  // namespace chrome
-
-#endif  // CHROME_BROWSER_UI_COCOA_OBSOLETE_OS_H_