Enable MSVC warning for unused locals.

chrome/installer/setup/setup_main.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/installer/setup/setup_main.h"
 
 #include <windows.h>
 #include <msi.h>
 #include <shellapi.h>
 #include <shlobj.h>
@@ skipping 1514 matching lines @@
                    << product.distribution()->GetDisplayName()
                    << " is already installed.";
         higher_products |= (1 << product.distribution()->GetType());
       }
     }
 
     if (higher_products != 0) {
       COMPILE_ASSERT(BrowserDistribution::NUM_TYPES == 4,
                      add_support_for_new_products_here_);
       const uint32 kBrowserBit = 1 << BrowserDistribution::CHROME_BROWSER;
-      const uint32 kAppHostBit = 1 << BrowserDistribution::CHROME_APP_HOST;
       int message_id = 0;
 
       proceed_with_installation = false;
       install_status = HIGHER_VERSION_EXISTS;
       switch (higher_products) {
         case kBrowserBit:
           message_id = IDS_INSTALL_HIGHER_VERSION_BASE;
           break;
         default:
           message_id = IDS_INSTALL_HIGHER_VERSION_APP_LAUNCHER_BASE;
@@ skipping 286 matching lines @@
     // Note that we allow the status installer::UNINSTALL_REQUIRES_REBOOT
     // to pass through, since this is only returned on uninstall which is
     // never invoked directly by Google Update.
     return_code = InstallUtil::GetInstallReturnCode(install_status);
   }
 
   VLOG(1) << "Installation complete, returning: " << return_code;
 
   return return_code;
 }