Move some XDG code from chrome to base.

chrome/common/chrome_paths_internal.h

 // Copyright (c) 2006-2008 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_CHROME_PATHS_INTERNAL_H_
 #define CHROME_COMMON_CHROME_PATHS_INTERNAL_H_
 
 #include "build/build_config.h"
 #include "base/file_path.h"
 
 namespace chrome {
 
 // Get the path to the user's data directory, regardless of whether
 // DIR_USER_DATA has been overridden by a command-line option.
 bool GetDefaultUserDataDirectory(FilePath* result);
 
 // This returns the base directory in which Chrome Frame stores user profiles.
 // Note that this cannot be wrapped in a preprocessor define since
 // CF and Google Chrome want to share the same binaries.
 bool GetChromeFrameUserDataDirectory(FilePath* result);
 
-#if defined(OS_LINUX)
-// Get the path to the user's cache directory.
-bool GetUserCacheDirectory(FilePath* result);
-#endif
-
 // Get the path to the user's documents directory.
 bool GetUserDocumentsDirectory(FilePath* result);
 
 // Get the path to the user's downloads directory.
 bool GetUserDownloadsDirectory(FilePath* result);
 
 // The path to the user's desktop.
 bool GetUserDesktop(FilePath* result);
 
 #if defined(OS_MACOSX)
 // The "versioned directory" is a directory in the browser .app bundle.  It
 // contains the bulk of the application, except for the things that the system
 // requires be located at spepcific locations.  The versioned directory is
 // in the .app at Contents/Versions/w.x.y.z.
 FilePath GetVersionedDirectory();
 
 // Most of the application is further contained within the framework.  The
 // framework bundle is located within the versioned directory at a specific
 // path.  The only components in the versioned directory not included in the
 // framework are things that also depend on the framework, such as the helper
 // app bundle.
 FilePath GetFrameworkBundlePath();
 #endif  // OS_MACOSX
 
 }  // namespace chrome
 
 #endif  // CHROME_COMMON_CHROME_PATHS_INTERNAL_H_