[Reland] Enable AutoResize for Constrained Web Dialogs for Mac.

chrome/browser/ui/cocoa/profiles/profile_signin_confirmation_dialog_cocoa.mm

 // Copyright 2014 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/profiles/profile_signin_confirmation_dialog_cocoa.h"
 
 #include "base/message_loop/message_loop.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/browser_window.h"
@@ skipping 41 matching lines @@
                  delegate:delegate
       closeDialogCallback:closeDialogCallback
      offerProfileCreation:offer_profile_creation]);
 
   // Setup the constrained window that will show the view.
   base::scoped_nsobject<NSWindow> window([[ConstrainedWindowCustomWindow alloc]
       initWithContentRect:[[controller_ view] bounds]]);
   [[window contentView] addSubview:[controller_ view]];
   base::scoped_nsobject<CustomConstrainedWindowSheet> sheet(
       [[CustomConstrainedWindowSheet alloc] initWithCustomWindow:window]);
-  window_.reset(new ConstrainedWindowMac(this, web_contents, sheet));
+  window_ = CreateAndShowWebModalDialogMac(this, web_contents, sheet);
 }
 
 ProfileSigninConfirmationDialogCocoa::~ProfileSigninConfirmationDialogCocoa() {
 }
 
 // static
 void ProfileSigninConfirmationDialogCocoa::Show(
     Browser* browser,
     content::WebContents* web_contents,
     Profile* profile,
     const std::string& username,
     ui::ProfileSigninConfirmationDelegate* delegate) {
   ui::CheckShouldPromptForNewProfile(
       profile, base::Bind(ShowDialog, browser, web_contents, profile, username,
                           delegate));
 }
 
 void ProfileSigninConfirmationDialogCocoa::Close() {
   window_->CloseWebContentsModalDialog();
 }
 
 void ProfileSigninConfirmationDialogCocoa::OnConstrainedWindowClosed(
     ConstrainedWindowMac* window) {
   base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }