Only allow installation of extensions/apps with gallery update url via download from gallery

chrome/common/extensions/extension_constants.cc

 // Copyright (c) 2009 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/common/extensions/extension_constants.h"
 
 namespace extension_manifest_keys {
 
 const wchar_t* kAllFrames = L"all_frames";
 const wchar_t* kBackground = L"background_page";
@@ skipping 238 matching lines @@
     "Invalid value for 'omnibox_keyword'.";
 const char* kOmniboxExperimental =
     "You must request the 'experimental' permission in order to use the"
     " omnibox API.";
 }  // namespace extension_manifest_errors
 
 namespace extension_urls {
 const char* kGalleryBrowsePrefix = "https://chrome.google.com/extensions";
 const char* kGalleryDownloadPrefix =
     "https://clients2.googleusercontent.com/crx/download";
+const char* kGalleryUpdateURL =
+    "http://clients2.google.com/service/update2/crx";
 const char* kMiniGalleryBrowsePrefix = "https://tools.google.com/chrome/";
 const char* kMiniGalleryDownloadPrefix = "https://dl-ssl.google.com/chrome/";
 }
 
 namespace extension_filenames {
 const char* kTempExtensionName = "CRX_INSTALL";
 
 // The file to write our decoded images to, relative to the extension_path.
 const char* kDecodedImagesFilename = "DECODED_IMAGES";
 
 // The file to write our decoded message catalogs to, relative to the
 // extension_path.
 const char* kDecodedMessageCatalogsFilename = "DECODED_MESSAGE_CATALOGS";
 }