MacViews: Unify web contents modal dialog types

chrome/browser/ui/cocoa/certificate_viewer_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.
 
 #import "chrome/browser/ui/cocoa/certificate_viewer_mac.h"
 
 #include <Security/Security.h>
 #include <SecurityInterface/SFCertificatePanel.h>
 #include <vector>
 
@@ skipping 179 matching lines @@
 }
 
 - (void)makeSheetKeyAndOrderFront {
   [[overlayWindow_ attachedSheet] makeKeyAndOrderFront:nil];
 }
 
 - (void)updateSheetPosition {
   // NOOP
 }
 
+- (NSWindow*)sheetWindow {
+  return panel_;
+}
+
 - (void)onConstrainedWindowClosed {
   panel_.reset();
   constrainedWindow_.reset();
   [self release];
 }
 
 @end