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

base/file_util_posix.cc

Index: base/file_util_posix.cc
diff --git a/base/file_util_posix.cc b/base/file_util_posix.cc
index d9cbe0945e75fe3be45dd380affcf445c0051a25..9db41fe95b196c20e7541f66c9bf23809ade696d 100644
--- a/base/file_util_posix.cc
+++ b/base/file_util_posix.cc
@@ -14,6 +14,7 @@
 #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>
@@ -735,6 +736,15 @@ bool HasFileBeenModifiedSince(const FileEnumerator::FindInfo& find_info,
   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");