Fail gracefully if profile Temp dir can not be accessed.

chrome/common/extensions/extension_file_util.h

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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_COMMON_EXTENSIONS_EXTENSION_FILE_UTIL_H_
 #define CHROME_COMMON_EXTENSIONS_EXTENSION_FILE_UTIL_H_
 #pragma once
 
 #include <string>
 #include <map>
 
@@ skipping 57 matching lines @@
 // We need to reserve the namespace of entries that start with "_" for future
 // use by Chrome.
 // If any files or directories are found using "_" prefix and are not on
 // reserved list we return false, and set error message.
 bool CheckForIllegalFilenames(const FilePath& extension_path,
                               std::string* error);
 
 // Get a relative file path from a chrome-extension:// URL.
 FilePath ExtensionURLToRelativeFilePath(const GURL& url);
 
+// Get a path to a temp directory for unpacking an extension.
+// This is essentially PathService::Get(chrome::DIR_USER_DATA_TEMP, ...),
+// with a histogram that allows us to understand why it is failing.
+// Return an empty file path on failure.
+FilePath GetUserDataTempDir();
+
 }  // namespace extension_file_util
 
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_FILE_UTIL_H_