Add a group policy controlling which sites can install extensions.

chrome/browser/extensions/extension_browsertest.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/extensions/extension_browsertest.h"
 
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/file_path.h"
@@ skipping 285 matching lines @@
     FilePath crx_path = path;
     if (crx_path.Extension() != FILE_PATH_LITERAL(".crx")) {
       crx_path = PackExtension(path);
     }
     if (crx_path.empty())
       return NULL;
 
     scoped_refptr<CrxInstaller> installer(
         CrxInstaller::Create(service, install_ui));
     installer->set_expected_id(id);
-    installer->set_allow_off_store_install(true);
     installer->set_is_gallery_install(from_webstore);
+    if (!from_webstore) {
+      installer->set_off_store_install_allow_reason(
+          CrxInstaller::OffStoreInstallAllowedInTest);
+    }
 
     content::NotificationRegistrar registrar;
     registrar.Add(this, chrome::NOTIFICATION_CRX_INSTALLER_DONE,
                   content::Source<CrxInstaller>(installer.get()));
 
     installer->InstallCrx(crx_path);
 
     ui_test_utils::RunMessageLoop();
   }
 
@@ skipping 270 matching lines @@
     case content::NOTIFICATION_LOAD_STOP:
       VLOG(1) << "Got LOAD_STOP notification.";
       MessageLoopForUI::current()->Quit();
       break;
 
     default:
       NOTREACHED();
       break;
   }
 }