Use a uniform opaque type to represent web contents modal dialogs

chrome/browser/ui/cocoa/constrained_window/constrained_window_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/constrained_window/constrained_window_mac.h"
 
 #include "base/logging.h"
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/browser_window.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_sheet.h"
@@ skipping 58 matching lines @@
 }
 
 void ConstrainedWindowMac::FocusWebContentsModalDialog() {
 }
 
 void ConstrainedWindowMac::PulseWebContentsModalDialog() {
   [[ConstrainedWindowSheetController controllerForSheet:sheet_]
       pulseSheet:sheet_];
 }
 
-gfx::NativeWindow ConstrainedWindowMac::GetNativeWindow() {
-  NOTREACHED();
-  return nil;
+NativeWebContentsModalDialog ConstrainedWindowMac::GetNativeDialog() {
+  return sheet_.get();
 }
 
 void ConstrainedWindowMac::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   if (type != content::NOTIFICATION_WEB_CONTENTS_VISIBILITY_CHANGED) {
     NOTREACHED();
     return;
   }
 
   if (pending_show_) {
     pending_show_ = false;
     ShowWebContentsModalDialog();
   }
 }
 
 NSWindow* ConstrainedWindowMac::GetParentWindow() const {
   // Tab contents in a tabbed browser may not be inside a window. For this
   // reason use a browser window if possible.
   Browser* browser = chrome::FindBrowserWithWebContents(web_contents_);
   if (browser)
     return browser->window()->GetNativeWindow();
 
   return web_contents_->GetView()->GetTopLevelNativeWindow();
 }