Disable off-store extension installs by default.

chrome/browser/download/download_crx_util.h

 // 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, ...).
 
 #ifndef CHROME_BROWSER_DOWNLOAD_DOWNLOAD_CRX_UTIL_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_CRX_UTIL_H_
 
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 
 class CrxInstaller;
 class ExtensionInstallUI;
+class ExtensionService;
 class Profile;
 
 namespace content {
 class DownloadItem;
 }
 
 namespace download_crx_util {
 
 // Allow tests to install a mock extension install UI object, to fake
 // user clicks on the permissions dialog.  Each installed mock object
 // is only used once.  If you want to return a mock for two different
 // installs, you need to call this function once before the first
 // install, and again after the first install and before the second.
 void SetMockInstallUIForTesting(ExtensionInstallUI* mock_ui);
 
 // Returns true if the specified download_item containing an extension should be
 // automatically installed. This is typically true in the case of webstore
 // installations.
-bool ShouldOpenExtensionDownload(const content::DownloadItem& download_item);
+bool ShouldOpenExtensionDownload(ExtensionService* service,
+                                 const content::DownloadItem& download_item);
 
 // Start installing a downloaded item item as a CRX (extension, theme, app,
 // ...).  The installer does work on the file thread, so the installation
 // is not complete when this function returns.  Returns the object managing
 // the installation.
 scoped_refptr<CrxInstaller> OpenChromeExtension(
     Profile* profile,
     const content::DownloadItem& download_item);
 
 }  // namespace download_crx_util
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_CRX_UTIL_H_