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

chrome/browser/download/download_extensions.h

+// 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.
+
+#ifndef CHROME_BROWSER_DOWNLOAD_DOWNLOAD_EXTENSIONS_H_
+#define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_EXTENSIONS_H_
+#pragma once
+
+#include <string>
+
+#include "base/file_path.h"
+
+namespace download_util {
+
+enum DownloadDangerLevel {
+  NotDangerous,
+  AllowOnUserGesture,
+  Dangerous
+};
+
+// Determine the download danger level of a file.
+DownloadDangerLevel GetFileDangerLevel(const FilePath& path);
+
+// Determine the download danger level using a file extension.
+DownloadDangerLevel GetFileExtensionDangerLevel(
+    const FilePath::StringType& extension);
+
+// True if the download danger level of the file is NotDangerous.
+bool IsFileSafe(const FilePath& path);
+
+// True if the download danger level of the extension is NotDangerous.
+bool IsFileExtensionSafe(const FilePath::StringType& extension);
+
+// Tests if we think the server means for this mime_type to be executable.
+bool IsExecutableMimeType(const std::string& mime_type);
+
+}  // namespace download_util
+
+#endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_EXTENSIONS_H_