Move some XDG code from chrome to base.

base/base_paths_posix.cc

 // 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.
 
+// This is really Posix minus Mac. Mac code is in base_paths_mac.mm.
+
 #include "base/base_paths.h"
 
 #include <unistd.h>
 
 #include "base/file_path.h"
 #include "base/file_util.h"
+#include "base/linux_util.h"
 #include "base/logging.h"
 #include "base/path_service.h"
-#include "base/string_piece.h"
+#include "base/scoped_ptr.h"
 #include "base/sys_string_conversions.h"
 
 namespace base {
 
 #if defined(OS_LINUX)
 const char kSelfExe[] = "/proc/self/exe";
 #elif defined(OS_FREEBSD)
 const char kSelfExe[] = "/proc/curproc/file";
 #endif
 
@@ skipping 25 matching lines @@
       // If that failed (maybe the build output is symlinked to a different
       // drive) try assuming the current directory is the source root.
       if (file_util::GetCurrentDirectory(&path) &&
           file_util::PathExists(path.Append("base/base_paths_posix.cc"))) {
         *result = path;
         return true;
       }
       LOG(ERROR) << "Couldn't find your source root.  "
                  << "Try running from your chromium/src directory.";
       return false;
+    case base::DIR_USER_CACHE:
+      scoped_ptr<base::EnvironmentVariableGetter> env(
+          base::EnvironmentVariableGetter::Create());
+      FilePath cache_dir(base::GetXDGDirectory(env.get(), "XDG_CACHE_HOME",
+                                               ".cache"));
+      *result = cache_dir;
+      return true;
   }
   return false;
 }
 
 }  // namespace base