[Downloads] Prevent dangerous files from being opened automatically.

chrome/browser/download/download_prefs.h

 // Copyright (c) 2012 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_PREFS_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_PREFS_H_
 
 #include <set>
 
 #include "base/files/file_path.h"
@@ skipping 48 matching lines @@
   bool IsDownloadPathManaged() const;
 
   // Returns true if there is at least one file extension registered
   // for auto-open.
   bool IsAutoOpenUsed() const;
 
   // Returns true if |path| should be opened automatically based on
   // |path.Extension()|.
   bool IsAutoOpenEnabledBasedOnExtension(const base::FilePath& path) const;
 
-  // Enables auto-open based on file extension. Returns true on success.
-  // TODO(phajdan.jr): Add WARN_UNUSED_RESULT here.
+  // Enables automatically opening all downloads with the same file type as
+  // |file_name|. Returns true on success. The call may fail if |file_name|
+  // either doesn't have an extension (hence the file type cannot be
+  // determined), or if the file type is one that is disallowed from being
+  // opened automatically. See IsAllowedToOpenAutomatically() for details on the
+  // latter.
   bool EnableAutoOpenBasedOnExtension(const base::FilePath& file_name);
 
   // Disables auto-open based on file extension.
   void DisableAutoOpenBasedOnExtension(const base::FilePath& file_name);
 
 #if defined(OS_WIN) || defined(OS_LINUX) || \
     (defined(OS_MACOSX) && !defined(OS_IOS))
   // Store the user preference to disk. If |should_open| is true, also disable
   // the built-in PDF plugin. If |should_open| is false, enable the PDF plugin.
   void SetShouldOpenPdfInSystemReader(bool should_open);
@@ skipping 26 matching lines @@
 
 #if defined(OS_WIN) || defined(OS_LINUX) || \
     (defined(OS_MACOSX) && !defined(OS_IOS))
   bool should_open_pdf_in_system_reader_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(DownloadPrefs);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_PREFS_H_