Disable off-store extension installs by default.

chrome/browser/download/download_crx_util.cc

Index: chrome/browser/download/download_crx_util.cc
diff --git a/chrome/browser/download/download_crx_util.cc b/chrome/browser/download/download_crx_util.cc
index a34ebecc316194cb969a4628ac65f3533cd9389d..af6cb5d3e637ee4f41b874fddd66bb6a99a63b96 100644
--- a/chrome/browser/download/download_crx_util.cc
+++ b/chrome/browser/download/download_crx_util.cc
@@ -51,9 +51,11 @@ 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;