Fixed crash in the proxy. Reference has been passed between threads,

chrome/service/cloud_print/cloud_print_proxy.cc

 // 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.
 
 #include "chrome/service/cloud_print/cloud_print_proxy.h"
 
 #include "base/command_line.h"
 #include "base/path_service.h"
 #include "base/process_util.h"
 #include "base/values.h"
@@ skipping 170 matching lines @@
   info->email.clear();
   if (enabled_)
     info->email = user_email();
   info->proxy_id = proxy_id_;
   // If the Cloud Print service is not enabled, we may need to read the old
   // value of proxy_id from prefs.
   if (info->proxy_id.empty())
     service_prefs_->GetString(prefs::kCloudPrintProxyId, &info->proxy_id);
 }
 
-// Notification methods from the backend. Called on UI thread.
-void CloudPrintProxy::OnPrinterListAvailable(
-    const printing::PrinterList& printer_list) {
-  DCHECK(CalledOnValidThread());
-  // We could potentially show UI here allowing the user to select which
-  // printers to register. For now, we just register all.
-  backend_->RegisterPrinters(printer_list);
-}
-
 void CloudPrintProxy::OnAuthenticated(
     const std::string& robot_oauth_refresh_token,
     const std::string& robot_email,
     const std::string& user_email) {
   DCHECK(CalledOnValidThread());
   service_prefs_->SetString(prefs::kCloudPrintRobotRefreshToken,
                             robot_oauth_refresh_token);
   service_prefs_->SetString(prefs::kCloudPrintRobotEmail,
                             robot_email);
   // If authenticating from a robot, the user email will be empty.
@@ skipping 32 matching lines @@
   }
 }
 
 void CloudPrintProxy::Shutdown() {
   DCHECK(CalledOnValidThread());
   if (backend_.get())
     backend_->Shutdown();
   backend_.reset();
 }