Firefox overlay is seen opened even if Import Overlay is Cancelled.

chrome/browser/ui/cocoa/importer/import_lock_dialog_cocoa.mm

 // Copyright (c) 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.
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 18 matching lines @@
       IDS_IMPORTER_LOCK_TEXT)];
   [lock_alert setMessageText:l10n_util::GetNSStringWithFixup(
       IDS_IMPORTER_LOCK_TITLE)];
 
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE,
       base::Bind(callback, [lock_alert runModal] == NSAlertFirstButtonReturn));
   content::RecordAction(UserMetricsAction("ImportLockDialogCocoa_Shown"));
 }
 
+void HideImportLockDialog() {
+  // This code path is not needed for MAC ,plz refer Issue:2769383002 for
+  // Details.

[Ilya Sherman, 2017/03/30 22:14:32]

nit: I'd rephrase this a bit to something like "This code path is not needed for
Mac, as the user must explicitly close the sheet before any situation can arise
in which we'd need to close it programmatically.  See https://crbug.com/672428
for more details.  (Of note, "Mac" is used for the OS, "MAC" is used for "MAC
addresses".)

[nikhil.sahni, 2017/03/31 15:21:25]

Done.

+}
+
 }  // namespace importer