Enable MSVC warning for unused locals.

cloud_print/service/win/cloud_print_service.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.
 
+// Work around warning in atlbase.h
+// https://connect.microsoft.com/VisualStudio/feedback/details/1032199/atlbase-h-gives-warning-c4189-when-compiling-with-atl-no-com-support
+#pragma warning(push)
+#pragma warning(disable:4189)
 #include <atlbase.h>
+#pragma warning(pop)
 #include <security.h>
 
 #include <iomanip>
 #include <iostream>
 #include <iterator>
 #include <string>
 #include <vector>
 
 #include "base/at_exit.h"
 #include "base/bind.h"
@@ skipping 311 matching lines @@
     *user_data_dir = setup.user_data_dir();
     *printers = setup.printers();
     return S_OK;
   }
 
   HRESULT SetupServiceState(const base::FilePath& user_data_dir,
                             const std::vector<std::string>& printers) {
     base::FilePath file = user_data_dir.Append(chrome::kServiceStateFileName);
 
     std::string contents;
+    base::ReadFileToString(file, &contents);
     ServiceState service_state;
-
-    bool is_valid = base::ReadFileToString(file, &contents) &&
-                    service_state.FromString(contents);
+    service_state.FromString(contents);
     std::string proxy_id = service_state.proxy_id();
 
     LOG(INFO) << file.value() << ": " << contents;
 
     base::string16 message =
         cloud_print::LoadLocalString(IDS_ADD_PRINTERS_USING_CHROME);
     std::cout << "\n" << message.c_str() << "\n" ;
     std::string new_contents =
         ChromeLauncher::CreateServiceStateFile(proxy_id, printers);
 
@@ skipping 62 matching lines @@
   settings.logging_dest = logging::LOG_TO_SYSTEM_DEBUG_LOG;
   logging::InitLogging(settings);
 
   logging::SetMinLogLevel(
       command_line->HasSwitch(switches::kEnableLogging) ?
       logging::LOG_INFO : logging::LOG_FATAL);
 
   return _AtlModule.WinMain(0);
 }