Fix a crash that could occur if the user closed a tab with an uncommitted search navigation that we…

chrome/browser/google/google_url_tracker_map_entry.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/google/google_url_tracker_map_entry.h"
 
 #include "chrome/browser/google/google_url_tracker.h"
 #include "chrome/browser/google/google_url_tracker_infobar_delegate.h"
 #include "chrome/browser/infobars/infobar.h"
 #include "chrome/common/chrome_notification_types.h"
@@ skipping 29 matching lines @@
 
 void GoogleURLTrackerMapEntry::SetInfoBar(
     GoogleURLTrackerInfoBarDelegate* infobar) {
   DCHECK(!infobar_);
   infobar_ = infobar;
   registrar_.Add(this, chrome::NOTIFICATION_TAB_CONTENTS_INFOBAR_REMOVED,
                  content::Source<InfoBarTabHelper>(infobar_helper_));
 }
 
 void GoogleURLTrackerMapEntry::Close(bool redo_search) {
-  if (infobar_)
+  if (infobar_) {
     infobar_->Close(redo_search);
-  else
+  } else {
+    // WARNING: |infobar_helper_| may point to a deleted object.  Do not
+    // dereference it!  See GoogleURLTracker::OnTabClosed().
     google_url_tracker_->DeleteMapEntryForHelper(infobar_helper_);
+  }
   // WARNING: At this point |this| has been deleted!
 }