Delete PrintingUIWebContentsObserver on UI thread.

chrome/browser/printing/print_job_worker.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/printing/print_job_worker.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/compiler_specific.h"
@@ skipping 87 matching lines @@
   if (ask_user_for_settings && destination_.get() == NULL) {
     BrowserThread::PostTask(
         BrowserThread::UI, FROM_HERE,
         base::Bind(&HoldRefCallback, make_scoped_refptr(owner_),
                    base::Bind(&PrintJobWorker::GetSettingsWithUI,
                               base::Unretained(this),
                               base::Passed(&web_contents_observer),
                               document_page_count,
                               has_selection)));
   } else {
+    BrowserThread::DeleteSoon(
+        BrowserThread::UI, FROM_HERE, web_contents_observer.release());
     BrowserThread::PostTask(
         BrowserThread::UI, FROM_HERE,
         base::Bind(&HoldRefCallback, make_scoped_refptr(owner_),
                    base::Bind(&PrintJobWorker::UseDefaultSettings,
                               base::Unretained(this))));
   }
 }
 
 void PrintJobWorker::SetSettings(
     const base::DictionaryValue* const new_settings) {
@@ skipping 271 matching lines @@
                               document_,
                               scoped_refptr<PrintedPage>()));
   Cancel();
 
   // Makes sure the variables are reinitialized.
   document_ = NULL;
   page_number_ = PageNumber::npos();
 }
 
 }  // namespace printing