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

chrome/service/cloud_print/cloud_print_proxy.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 CHROME_SERVICE_CLOUD_PRINT_CLOUD_PRINT_PROXY_H_
 #define CHROME_SERVICE_CLOUD_PRINT_CLOUD_PRINT_PROXY_H_
 #pragma once
 
 #include <string>
 
@@ skipping 34 matching lines @@
       const std::string& user_email);
   void DisableForUser();
   // Returns the proxy info.
   void GetProxyInfo(cloud_print::CloudPrintProxyInfo* info);
 
   const std::string& user_email() const {
     return user_email_;
   }
 
   // CloudPrintProxyFrontend implementation. Called on UI thread.
-  virtual void OnPrinterListAvailable(
-      const printing::PrinterList& printer_list);
   virtual void OnAuthenticated(const std::string& robot_oauth_refresh_token,
                                const std::string& robot_email,
                                const std::string& user_email);
   virtual void OnAuthenticationFailed();
   virtual void OnPrintSystemUnavailable();
 
  protected:
   void Shutdown();
   bool CreateBackend();
 
@@ skipping 13 matching lines @@
   // successful authentication with the Cloud Print service.
   bool enabled_;
   // This is initialized after a successful call to one of the Enable* methods.
   // It is not cleared in DisableUser.
   std::string proxy_id_;
 
   DISALLOW_COPY_AND_ASSIGN(CloudPrintProxy);
 };
 
 #endif  // CHROME_SERVICE_CLOUD_PRINT_CLOUD_PRINT_PROXY_H_