Minor cleanup to how infobars handle expiry:

chrome/browser/api/infobars/infobar_delegate.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/api/infobars/infobar_delegate.h"
 
 #include "base/logging.h"
 #include "build/build_config.h"
 #include "chrome/browser/api/infobars/infobar_service.h"
 #include "content/public/browser/navigation_controller.h"
@@ skipping 80 matching lines @@
 }
 
 TranslateInfoBarDelegate* InfoBarDelegate::AsTranslateInfoBarDelegate() {
   return NULL;
 }
 
 InfoBarDelegate::InfoBarDelegate(InfoBarService* infobar_service)
     : contents_unique_id_(0),
       owner_(infobar_service) {
   if (infobar_service)
-    StoreActiveEntryUniqueID(infobar_service);
+    StoreActiveEntryUniqueID();
 }
 
-void InfoBarDelegate::StoreActiveEntryUniqueID(
-    InfoBarService* infobar_service) {
+void InfoBarDelegate::StoreActiveEntryUniqueID() {
+  content::WebContents* web_contents = owner_->GetWebContents();
+  DCHECK(web_contents);
   NavigationEntry* active_entry =
-      infobar_service->GetWebContents()->GetController().GetActiveEntry();
+      web_contents->GetController().GetActiveEntry();
   contents_unique_id_ = active_entry ? active_entry->GetUniqueID() : 0;
 }
 
 bool InfoBarDelegate::ShouldExpireInternal(
     const content::LoadCommittedDetails& details) const {
+  // NOTE: If you change this, be sure to check and adjust the behavior of
+  // anyone who overrides this as necessary!
   return (contents_unique_id_ != details.entry->GetUniqueID()) ||
       (content::PageTransitionStripQualifier(
           details.entry->GetTransitionType()) ==
               content::PAGE_TRANSITION_RELOAD);
 }
 
 void InfoBarDelegate::RemoveSelf() {
   if (owner_)
     owner_->RemoveInfoBar(this);  // Clears |owner_|.
 }