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

chrome/browser/download/download_prefs.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.
 
 #include "chrome/browser/download/download_prefs.h"
 
 #include "base/file_util.h"
 #include "base/string_split.h"
 #include "base/string_util.h"
 #include "base/sys_string_conversions.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/browser_thread.h"
+#include "chrome/browser/download/download_extensions.h"
 #include "chrome/browser/download/download_util.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/common/pref_names.h"
 
 DownloadPrefs::DownloadPrefs(PrefService* prefs) : prefs_(prefs) {
   prompt_for_download_.Init(prefs::kPromptForDownload, prefs, NULL);
   download_path_.Init(prefs::kDownloadDefaultDirectory, prefs, NULL);
 
   // We store any file extension that should be opened automatically at
   // download completion in this pref.
   std::string extensions_to_open =
       prefs->GetString(prefs::kDownloadExtensionsToOpen);
   std::vector<std::string> extensions;
   base::SplitString(extensions_to_open, ':', &extensions);
 
   for (size_t i = 0; i < extensions.size(); ++i) {
 #if defined(OS_POSIX)
     FilePath path(extensions[i]);
 #elif defined(OS_WIN)
     FilePath path(UTF8ToWide(extensions[i]));
 #endif
-    if (!extensions[i].empty() && !download_util::IsExecutableFile(path))
+    if (!extensions[i].empty() && download_util::IsFileSafe(path))
       auto_open_.insert(path.value());
   }
 }
 
 DownloadPrefs::~DownloadPrefs() {
   SaveAutoOpenState();
 }
 
 // static
 void DownloadPrefs::RegisterUserPrefs(PrefService* prefs) {
@@ skipping 36 matching lines @@
     const FilePath::StringType& extension) const {
   return auto_open_.find(extension) != auto_open_.end();
 }
 
 bool DownloadPrefs::EnableAutoOpenBasedOnExtension(const FilePath& file_name) {
   FilePath::StringType extension = file_name.Extension();
   if (extension.empty())
     return false;
   DCHECK(extension[0] == FilePath::kExtensionSeparator);
   extension.erase(0, 1);
-  if (download_util::IsExecutableExtension(extension))
+  if (!download_util::IsFileExtensionSafe(extension))
     return false;
 
   auto_open_.insert(extension);
   SaveAutoOpenState();
   return true;
 }
 
 void DownloadPrefs::DisableAutoOpenBasedOnExtension(const FilePath& file_name) {
   FilePath::StringType extension = file_name.Extension();
   if (extension.empty())
@@ skipping 30 matching lines @@
     extensions.erase(extensions.size() - 1);
 
   prefs_->SetString(prefs::kDownloadExtensionsToOpen, extensions);
 }
 
 bool DownloadPrefs::AutoOpenCompareFunctor::operator()(
     const FilePath::StringType& a,
     const FilePath::StringType& b) const {
   return FilePath::CompareLessIgnoreCase(a, b);
 }