Disable off-store extension installs by default.

chrome/browser/download/download_crx_util.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.
 //
 // Download code which handles CRX files (extensions, themes, apps, ...).
 
 #include "chrome/browser/download/download_util.h"
 #include "chrome/browser/extensions/crx_installer.h"
 #include "chrome/browser/extensions/extension_install_ui.h"
 #include "chrome/browser/extensions/extension_service.h"
@@ skipping 33 matching lines @@
 }
 
 }  // namespace
 
 // Tests can call this method to inject a mock ExtensionInstallUI
 // to be used to confirm permissions on a downloaded CRX.
 void SetMockInstallUIForTesting(ExtensionInstallUI* mock_ui) {
   mock_install_ui_for_testing = mock_ui;
 }
 
-bool ShouldOpenExtensionDownload(const DownloadItem& download_item) {
+bool ShouldOpenExtensionDownload(ExtensionService* service,
+                                 const DownloadItem& download_item) {
   if (extensions::switch_utils::IsOffStoreInstallEnabled() ||
-      WebstoreInstaller::GetAssociatedApproval(download_item)) {
+      (service && service->IsDownloadFromGallery(
+          download_item.GetURL(), download_item.GetReferrerUrl()))) {
     return true;
   } else {
     return false;
   }
 }
 
 scoped_refptr<CrxInstaller> OpenChromeExtension(
     Profile* profile,
     const DownloadItem& download_item) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
@@ skipping 23 matching lines @@
       installer->set_original_download_url(download_item.GetOriginalUrl());
     installer->set_allow_silent_install(is_gallery_download);
     installer->set_install_cause(extension_misc::INSTALL_CAUSE_USER_DOWNLOAD);
     installer->InstallCrx(download_item.GetFullPath());
   }
 
   return installer;
 }
 
 }  // namespace download_crx_util