infobars: Remove the downcast AsAlternateNavInfoBarDelegate() function.

chrome/browser/ui/views/infobars/alternate_nav_infobar_view.cc

 // 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/views/infobars/alternate_nav_infobar_view.h"
 
 #include "base/logging.h"
 #include "chrome/browser/event_disposition.h"
 #include "chrome/browser/ui/omnibox/alternate_nav_infobar_delegate.h"
 #include "ui/views/controls/label.h"
@@ skipping 68 matching lines @@
   if (!owned())
     return;  // We're closing; don't call anything, it might access the owner.
   DCHECK(link_ != NULL);
   DCHECK_EQ(link_, source);
   if (GetDelegate()->LinkClicked(
       chrome::DispositionFromEventFlags(event_flags)))
     RemoveSelf();
 }
 
 AlternateNavInfoBarDelegate* AlternateNavInfoBarView::GetDelegate() {
-  return delegate()->AsAlternateNavInfoBarDelegate();
+  return static_cast<AlternateNavInfoBarDelegate*>(delegate());
 }