Use realpath() to find the path to the extension unpack dir on posix systems.

base/file_util_posix.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 "base/file_util.h"
 
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <fnmatch.h>
 #include <libgen.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/errno.h>
 #include <sys/mman.h>
+#include <sys/param.h>

[Lei Zhang, 2010/05/12 18:53:32]

nit: My Linux man page says this should be <limits.h> ?

[Sam Kerner (Chrome), 2010/05/12 20:02:57]

I used the mac man page, then tested on linux...  Will send you a CL with an
update shortly.

 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <time.h>
 #include <unistd.h>
 
 #if defined(OS_MACOSX)
 #include <AvailabilityMacros.h>
 #else
 #include <glib.h>
@@ skipping 701 matching lines @@
   data_ = NULL;
   length_ = 0;
   file_ = base::kInvalidPlatformFileValue;
 }
 
 bool HasFileBeenModifiedSince(const FileEnumerator::FindInfo& find_info,
                               const base::Time& cutoff_time) {
   return find_info.stat.st_mtime >= cutoff_time.ToTimeT();
 }
 
+bool RealPath(const FilePath& path, FilePath* real_path) {
+  FilePath::CharType buf[PATH_MAX];
+  if (!realpath(path.value().c_str(), buf))
+    return false;
+
+  *real_path = FilePath(buf);
+  return true;
+}
+
 #if !defined(OS_MACOSX)
 bool GetTempDir(FilePath* path) {
   const char* tmp = getenv("TMPDIR");
   if (tmp)
     *path = FilePath(tmp);
   else
     *path = FilePath("/tmp");
   return true;
 }
 
@@ skipping 60 matching lines @@
   if (HANDLE_EINTR(close(infile)) < 0)
     result = false;
   if (HANDLE_EINTR(close(outfile)) < 0)
     result = false;
 
   return result;
 }
 #endif  // defined(OS_MACOSX)
 
 } // namespace file_util