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

chrome/browser/download/download_item.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_item.h"
 
 #include "app/l10n_util.h"
 #include "base/basictypes.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/stringprintf.h"
 #include "base/timer.h"
 #include "base/utf_string_conversions.h"
 #include "net/base/net_util.h"
 #include "chrome/browser/browser_thread.h"
+#include "chrome/browser/download/download_extensions.h"
 #include "chrome/browser/download/download_file_manager.h"
 #include "chrome/browser/download/download_history.h"
 #include "chrome/browser/download/download_manager.h"
 #include "chrome/browser/download/download_prefs.h"
 #include "chrome/browser/download/download_util.h"
 #include "chrome/browser/history/download_create_info.h"
 #include "chrome/browser/platform_util.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/extensions/extension.h"
@@ skipping 163 matching lines @@
 void DownloadItem::UpdateObservers() {
   FOR_EACH_OBSERVER(Observer, observers_, OnDownloadUpdated(this));
 }
 
 void DownloadItem::NotifyObserversDownloadFileCompleted() {
   FOR_EACH_OBSERVER(Observer, observers_, OnDownloadFileCompleted(this));
 }
 
 bool DownloadItem::CanOpenDownload() {
   return !Extension::IsExtension(target_name_) &&
-      !download_util::IsExecutableFile(target_name_);
+      download_util::IsFileSafe(target_name_);
 }
 
 bool DownloadItem::ShouldOpenFileBasedOnExtension() {
   return download_manager_->ShouldOpenFileBasedOnExtension(
       GetUserVerifiedFilePath());
 }
 
 void DownloadItem::OpenFilesBasedOnExtension(bool open) {
   DownloadPrefs* prefs = download_manager_->download_prefs();
   if (open)
@@ skipping 279 matching lines @@
         target_name_.value().c_str(),
         full_path().value().c_str(),
         DebugSafetyStateString(safety_state()));
   }
 
   description += base::StringPrintf(" state = %s }",
                                     DebugDownloadStateString(state()));
 
   return description;
 }