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

chrome/common/extensions/extension_constants.h

Index: chrome/common/extensions/extension_constants.h
diff --git a/chrome/common/extensions/extension_constants.h b/chrome/common/extensions/extension_constants.h
index 35c455589b3ce236b2f2a8758ba7d5899d45bad3..330f6d14db0e0f77242e0833aa4c5971982a5362 100644
--- a/chrome/common/extensions/extension_constants.h
+++ b/chrome/common/extensions/extension_constants.h
@@ -172,6 +172,9 @@ namespace extension_urls {
   extern const char* kGalleryBrowsePrefix;
   extern const char* kGalleryDownloadPrefix;
 
+  // The update url used by gallery/webstore extensions.
+  extern const char* kGalleryUpdateURL;
+
   // Same thing for the "minigallery". The minigallery is the temporary static
   // themes gallery that we put up when we launched themes.
   extern const char* kMiniGalleryBrowsePrefix;