Modify the "dangerous download" algorithm as follows. Original patch by Pier...

chrome/browser/download/download_util.cc

 // Copyright (c) 2010 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 utility implementation
 
 #include "chrome/browser/download/download_util.h"
 
 #if defined(OS_WIN)
 #include <shobjidl.h>
 #endif
 #include <string>
 
 #include "app/l10n_util.h"
 #include "app/resource_bundle.h"
 #include "base/file_util.h"
 #include "base/i18n/rtl.h"
 #include "base/i18n/time_formatting.h"
 #include "base/path_service.h"
 #include "base/singleton.h"
 #include "base/string16.h"
 #include "base/string_number_conversions.h"
 #include "base/stringprintf.h"
 #include "base/sys_string_conversions.h"
 #include "base/thread_restrictions.h"
 #include "base/utf_string_conversions.h"
 #include "base/values.h"
 #include "base/win/windows_version.h"
 #include "chrome/browser/browser_thread.h"
+#include "chrome/browser/download/download_extensions.h"
 #include "chrome/browser/download/download_item.h"
 #include "chrome/browser/download/download_item_model.h"
 #include "chrome/browser/download/download_manager.h"
 #include "chrome/browser/extensions/crx_installer.h"
 #include "chrome/browser/extensions/extension_install_ui.h"
 #include "chrome/browser/extensions/extensions_service.h"
 #include "chrome/browser/history/download_create_info.h"
 #include "chrome/browser/net/chrome_url_request_context.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/renderer_host/resource_dispatcher_host.h"
@@ skipping 672 matching lines @@
   FilePath::StringType file_name;
   base::SStringPrintf(
       &file_name,
       PRFilePathLiteral FILE_PATH_LITERAL(".crdownload"),
       suggested_path.value().c_str());
   return FilePath(file_name);
 }
 
 // TODO(erikkay,phajdan.jr): This is apparently not being exercised in tests.
 bool IsDangerous(DownloadCreateInfo* info, Profile* profile) {
-  // Downloads can be marked as dangerous for two reasons:
-  // a) They have a dangerous-looking filename
-  // b) They are an extension that is not from the gallery
-  if (IsExecutableFile(info->suggested_path.BaseName())) {
+  DownloadDangerLevel danger_level = GetFileDangerLevel(
+      info->suggested_path.BaseName());
+
+  if (danger_level == Dangerous) {
+    return true;
+  } else if (danger_level == AllowOnUserGesture && !info->has_user_gesture) {
     return true;
   } else if (info->is_extension_install) {
     ExtensionsService* service = profile->GetExtensionsService();
     if (!service ||
         !service->IsDownloadFromGallery(info->url, info->referrer_url)) {
+      // Extensions that are not from the gallery are considered dangerous.
       return true;
     }
   }
+
   return false;
 }
 
 }  // namespace download_util