Attempt at fixing crash. It looks like the printing code can delete

content/common/notification_type.h

 // Copyright (c) 2011 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.
 
 #ifndef CONTENT_COMMON_NOTIFICATION_TYPE_H_
 #define CONTENT_COMMON_NOTIFICATION_TYPE_H_
 #pragma once
 
 // This file describes various types used to describe and filter notifications
 // that pass through the NotificationService.
@@ skipping 774 matching lines @@
     GOOGLE_URL_UPDATED,
 
     // Printing ----------------------------------------------------------------
 
     // Notification from PrintJob that an event occured. It can be that a page
     // finished printing or that the print job failed. Details is
     // PrintJob::EventDetails. Source is a PrintJob.
     PRINT_JOB_EVENT,
 
     // Sent when a PrintJob has been released.
-    // Source is the TabContents that holds the print job.
+    // Source is the TabContentsWrapper that holds the print job.
     PRINT_JOB_RELEASED,
 
     // Shutdown ----------------------------------------------------------------
 
     // Sent on the browser IO thread when an net::URLRequestContext is released
     // by its owning Profile.  The source is a pointer to the
     // net::URLRequestContext.
     URL_REQUEST_CONTEXT_RELEASED,
 
     // Sent when WM_ENDSESSION has been received, after the browsers have been
@@ skipping 529 matching lines @@
 };
 
 inline bool operator==(NotificationType::Type a, NotificationType b) {
   return a == b.value;
 }
 inline bool operator!=(NotificationType::Type a, NotificationType b) {
   return a != b.value;
 }
 
 #endif  // CONTENT_COMMON_NOTIFICATION_TYPE_H_